Siblings Share Genes, But Rarely Personalities (2022)

Siblings Share Genes, But Rarely Personalities (1)

Brothers Eric (from left) and Tom Hoebbel have the same genes, but they couldn't be more different. Courtesy of Tom Hoebbel hide caption

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Courtesy of Tom Hoebbel

The fight happened a long time ago when they were still in school. But for both Tom and Eric Hoebbel, the fight was a defining event -- the kind of family story that gets trotted out for new acquaintances because it seems to convey something important.

Tom, as the story goes, was just back from college, and the two brothers were together in the kitchen late at night. They chatted aimlessly about school and sports. Then the conversation turned to money.

Tom's position was that money was inconsequential. "I said, 'I could just, you know, take out a dollar bill and burn it, and that wouldn't really matter,' " Tom says. But this idea horrified his brother. "A dollar bill is very valuable," says Eric. "Even if it's only $1, you can still do stuff with it."

But Tom persisted, and to demonstrate his seriousness, he removed a dollar from his pocket and literally set it on fire.

At which point, by all accounts, Eric completely and utterly freaked out.

"I was probably being held back," Eric says.

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There they were: Two brothers of roughly the same height and weight, with the same hair color and the same last name. But as they looked across the table from one another, Tom Hoebbel says, what they saw was unrecognizable. "I think he couldn't conceive why I would possibly do that, just like I couldn't conceive why it was such a big deal to him."

Today, Tom and Eric Hoebbel are middle-aged men, and their personalities and lives are radically different. Tom is an artist; Eric's a financial adviser. Tom is a former rebel who doesn't practice institutional religion; Eric's a joiner who goes to church almost every Sunday. Then, there is the wardrobe issue. Tom has one tie. Eric: 150.

The Hoebbels are an extreme example of a common occurrence: Many siblings have very different personalities. But to researchers, this is a puzzle. Siblings share both genes and environment. Why, then, are they often so different?

Breakthrough In Sibling Research

For most of history, psychologists thought of the study of siblings as backwater: Parenting was important -- siblings were not.

Then in the 1980s, a researcher named Robert Plomin published a surprising paper in which he reviewed the three main ways psychologists had studied siblings: physical characteristics, intelligence and personality. According to Plomin, in two of these areas, siblings were really quite similar.

Physically, siblings tended to differ somewhat, but they were a lot more similar on average when compared to children picked at random from the population. That's also true of cognitive abilities.

Siblings Share Genes, But Rarely Personalities (3)

Tom Hoebbel (left) became an artist, while Eric (right) chose finance. Courtesy of Tom Hoebbel hide caption

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Courtesy of Tom Hoebbel

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"The surprise," says Plomin, "is when you turn to personality."

Turns out that on tests that measure personality -- stuff like how extroverted you are, how conscientious -- siblings are practically like strangers.

"Children in the same family are more similar than children taken at random from the population," Plomin says, "but not much more."

In fact, in terms of personality, we are similar to our siblings only about 20 percent of the time. Given the fact that we share genes, homes, routines and parents, this makes no sense. What makes children in the same family so different?

Separating Genes From Environment

To come up with an answer, Plomin and other researchers did study after study. They were trying to tease out what role genes played in the personality differences they saw, and what role the environment played in those differences. When they began, they assumed, like everyone else, that being raised in the same environment would be one of the things that made children similar. This, however, is not what they found.

"The environment works in a very odd way," says Plomin. "It's making two children in the same family different from one another. Not similar to one another -- different."

The question was: Why is it that being raised in the same family pushes children in opposite directions in terms of personality?

No one knows for sure, but there are three major theories.

Theory One: Divergence

The first is a view popularized by a Darwin scholar named Frank Sulloway. In Sulloway's view, competition is the engine that pushes evolution -- just as in the wild. Therefore, in the context of a family, one of the main things that's happening is that children are competing for the time, love and attention of their parents.

"And when organisms compete," says Sulloway, "there tends to be a phenomenon that Darwin long ago identified in the origins of species called the principle of divergence. The role of divergence is basically to minimize competition so it's not direct. And that leads to specialization in different niches."

So if one child in a family seems to excel at academics, to avoid direct competition, the other child -- consciously or unconsciously -- will specialize in a different area, like socializing.

Sulloway says he saw a small version of this happen in his own family. His elder brother was a great tennis player, and he eventually became a professional tennis player. Sulloway says he never in his life was able to take a set from his brother. "And in the course of my high school experience, I discovered I was much better in track than in tennis," Sulloway says. So he switched. "It was a very conscious decision. I just was never going to be as good in tennis as he was."

Theory Two: Environment

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The second theory has a slightly confusing name; it's called the non-shared environment theory, and it essentially argues that though from the outside it appears that we are growing up in the same family as our siblings, in very important ways we really aren't. We are not experiencing the same thing.

"Children grow up in different families because most siblings differ in age, and so the timing with which you go through your family's [major events] is different," says Susan McHale, a researcher at Pennsylvania State University. "You know, a parent loses a job, parents get divorced. If you are three or five years behind your sibling, the experience of a 5-year-old whose parents get divorced is very different from the experience of a 9-year-old or a 10-year-old."

Also, McHale says, children in the same family are rarely treated the same by their parents, even if parents want to treat them the same.

"Children have different needs," McHale says. "They have different interests. They have different personalities that are eliciting different treatment from parents."

Theory Three: Exaggeration

The final theory is the comparison theory, which holds that families are essentially comparison machines that greatly exaggerate even minor differences between siblings.

Imagine, says McHale, two friendly children born in the same family. "One of those children is incredibly extroverted, and the other is just very sociable," says McHale. In the context of any other family, says McHale, the second child would be considered an extrovert. "But in this family," says McHale, "she's the introvert."

And once the introvert label is assigned -- even if in an absolute sense it's not really true -- it influences the choices that the child makes.

"And so we pick different groups of friends, we spend our time in different ways that only reinforces what may have been a very small difference to begin with," McHale says. "And, you know, once you get these forces feeding on one another, differences escalate over time."

Siblings Share Genes, But Rarely Personalities (4)

Tom and Eric Hoebbel with their father, who died in 1982. Courtesy of Tom Hoebbel hide caption

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Courtesy of Tom Hoebbel

Different Homes

So, why are Tom and Eric Hoebbel so different? Both said the answer was clear. In their case, it wasn't Darwinian. Eric especially was convinced he didn't gravitate toward the path he's on to be different from his brother.

"No, I don't think it was a reaction to him at all," Eric says.

Tom agrees.

Instead they point to the death of their father. When their father died, Tom was 17 and heading off to college -- but Eric was only 12. So, in a sense, they grew up in different homes. Tom, the radical, grew up in a secure, two-parent home. But Eric the financial planner, as Tom points out, spent many years as the only man in a house destabilized both emotionally and financially by death.

"And as he grew and went to college, I think maybe that was for him his primary motivation -- is to be the provider," Tom says.

So, this Thursday as you eat your turkey, look across the table. There, you may see a brother, a sister, a step-sibling, a twin. And maybe they're your friend, and maybe they're your enemy, but one thing is for certain: Their very existence has had a profound influence on your life.

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FAQs

Why do siblings share some traits but not others? ›

After all, kids get their genes from the same parents. But brothers and sisters don't look exactly alike because everyone (including parents) actually has two copies of most of their genes. And these copies can be different. Parents pass one of their two copies of each of their genes to their kids.

How can siblings have such different personalities? ›

The answer has to do with the fact that each parent actually has two different sets of genes. And that each parent passes only half of their genes to their child. And that the half that gets passed down is random. All of this together ensures that each child ends up with a different, unique set of genes.

Do siblings share the same personality? ›

Although studies have found that siblings tend, on average, to share physical characteristics and intelligence, they're “practically like strangers” when it comes to personality, Spiegel noted. “In fact,” said Spiegel, “in terms of personality, we are similar to our siblings only about 20 percent of the time.

Why can siblings often have very different personalities? ›

Q: Why are siblings so different? First of all, genetics can account for sibling differences. Siblings usually only share 50 percent of the DNA passed down from their parents. Second of all, even if siblings attend the same school, they may hang out in different crowds, which in turn influences their personality.

Why is my personality so different from my parents? ›

The reason is that personality traits are complex “phenotypes” that are thought to be influenced by many genes, and probably interactions across genes. Second, each parent is contributing a number of gene variants that contribute to this complicated genetic architecture of a given personality trait.

Who are you genetically closest to? ›

Ever since researchers sequenced the chimp genome in 2005, they have known that humans share about 99% of our DNA with chimpanzees, making them our closest living relatives.

How Being the youngest child affects personality? ›

The Youngest Child - “The Baby”

Just as with the oldest sibling, the youngest child often feels special and has a unique place in the family. They tend to be more rebellious and attention seeking, creative, social, and outgoing.

What determines personality type? ›

Scientists estimate that 20 to 60 percent of temperament is determined by genetics. Temperament, however, does not have a clear pattern of inheritance and there are not specific genes that confer specific temperamental traits.

Does the order of birth affect personality? ›

Birth order does not appear to influence personality in adults, according to several ambitious studies published in the past few years. This new wave of research relied on larger data sets and more robust statistical methods than earlier reports that claimed to find a relationship between birth order and personality.

What traits do siblings share? ›

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  • Mannerisms. So many moms may notice their little ones mimicking each other's mannerisms. ...
  • Sense Of Humor. ...
  • Academic Achievement. ...
  • They May Both Be Opinionated. ...
  • Shared Interests.
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What genes do fathers pass on? ›

Genetics of Inheritance

While moms pass down an X chromosome to their children—since women have two x chromosomes—dads pass down either an X or Y chromosome. The presence of a Y chromosome determines whether your baby's a boy or a girl.

Can DNA of siblings be different? ›

Because of recombination, siblings only share about 50 percent of the same DNA, on average, Dennis says. So while biological siblings have the same family tree, their genetic code might be different in at least one of the areas looked at in a given test. That's true even for fraternal twins.

Why are children from the same family so different? ›

Environmental variance not due to shared environment is called nonshared environment; this portion of environmental variance makes family members different from one another.

What is sister telepathy? ›

For those of you who have siblings, do you ever feel like you can read each others mind? My sister and I always jokingly say that we have “sister telepathy” when we finish each others sentences or we wear the same outfit on the same day.

Why do my children look so different? ›

Children can look so different from one another because they inherit a random mix of their parents' genes. Additionally, environmental factors such as diet and lifestyle choices can also impact a person's physical appearance.

Is personality inherited or learned? ›

Both genetics and environment play a part in the development of personality, although the specific degree to which each one plays a part often depends on the specific personality trait in question.

What parts of personality are genetic? ›

Some Traits Are Inherited

As far as why kids are sometimes exactly like or nothing like their parents, Bressette says studies show that personality traits can be inherited. “There are five traits that have a link to personality: extraversion, neuroticism, agreeableness, conscientiousness and openness.”

Is personality innate or learned? ›

A person's overall personality starts with an inborn disposition yet changes over time as a person interacts with their environment. In other words, a person's overall personality is made up of both natural (inborn) and adaptive (learned) traits.

Can siblings be 0% related? ›

Everyone is more or less 50% related to each of their parents, but could theoretically be anywhere from 0-100% related to their siblings.

Are you more like your mother or father? ›

You may have inherited your mother's eyes, but, genetically speaking, you use more DNA passed down from your father. That's the conclusion of a new study on mice that researchers say likely applies to all mammals.

What traits do daughters inherit from their fathers? ›

List of Traits which are Inherited from Father
  • Eye Colour. Dominant and recessive genes play a role in determining eye colour of the child. ...
  • Height. If the father is tall, there is more chance for the child to also be tall. ...
  • Dimples. ...
  • Fingerprints. ...
  • Lips. ...
  • Sneezing. ...
  • Teeth structure. ...
  • Mental disorders.
7 Dec 2018

What is the eldest daughter syndrome? ›

Eldest daughters are responsible, dutiful, thoughtful, expeditious and caring. Firstborns are more intelligent than their siblings, more proficient verbally and more motivated to perform. Yet at the same time they seriously doubt that they are good enough.

Which sibling is the most successful? ›

First-born kids tend to be leaders, like CEOS and founders, and are more likely to achieve traditional success. Middle-born children often embody a mix of the traits of older and younger siblings, and they're very relationship-focused.

What is the youngest child syndrome? ›

Youngest children are also often described as spoiled, willing to take unnecessary risks, and less intelligent than their oldest siblings. Psychologists have theorized that parents coddle youngest children.

What is the rarest personality type? ›

INFJ is the rarest personality type across the population, occurring in just 2% of the population. It is also the rarest personality type among men. INFJ stands for Introversion, Intuition, Feeling, and Judging.

What are the 4 types of personalities? ›

A study published in Nature Human Behaviour reveals that there are four personality types — average, reserved, role-model and self-centered — and these findings might change the thinking about personality in general.

Do personality types run in families? ›

Personality type is part nature, part nurture. Not only that, but nurture affects how our nature expresses itself. We're a product of our genetic families and the people who raised us, whether or not those are the same people.

What is the rarest birthday? ›

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  • February 29.
  • July 5.
  • May 26.
  • December 31.
  • April 13.
  • December 23.
  • April 1.
  • November 28.
22 Oct 2020

What is the rarest month to be born on? ›

According to the CDC, February is the least common birth month. That's also logical, seeing as nine months prior is May which marks longer, sunnier days, warmer temperatures and usually more outside activity. If you have any questions about conception, make sure to contact your provider.

What is the 2nd child syndrome? ›

Second child syndrome or middle child syndrome is when the second-born or middle-born child gets uncomfortable with the presence of their siblings. It can be due to the lack of importance or attention when the parents give more attention to younger children and give responsibilities to older siblings.

How Being the oldest child affects personality? ›

“Firstborn children can be goal-oriented, outspoken, stubborn, independent, and perfectionistic,” Smelser says, and when you look at the way firstborns are nurtured, it starts to make sense why. “These traits are often reinforced by parents through their interactions with the child,” she says.

What personality does the middle child have? ›

Characteristics of a Middle Child

They're good at being mediators and want fairness in situations. They're also trustworthy friends and work well as team members. Not as family-oriented as their siblings. They may have a stronger sense of not belonging than their siblings do.

Do First borns marry first borns? ›

According to the study, the best possible match is a firstborn female with a lastborn male, because their needs are in harmony with each other. A firstborn with another firstborn, Leman writes, is likely to be a power struggle.

Who is your closest blood relative? ›

List of who your nearest relative is
  • Husband, wife or civil partner (including cohabitee for more than 6 months).
  • Son or daughter.
  • Father or mother (an unmarried father must have parental responsibility in order to be nearest relative)
  • Brother or sister.
  • Grandparent.
  • Grandchild.
  • Uncle or aunt.
  • Nephew or niece.

Which parent does height come from? ›

The genetics of height

If they are tall or short, then your own height is said to end up somewhere based on the average heights between your two parents. Genes aren't the sole predictor of a person's height. In some instances, a child might be much taller than their parents and other relatives.

Is intelligence genetic? ›

Like most aspects of human behavior and cognition, intelligence is a complex trait that is influenced by both genetic and environmental factors.

Can Full siblings share 25% DNA? ›

On average full siblings will share about 50% of their DNA, while half siblings will share about 25% of their DNA. The actual amount may vary slightly since recombination will shuffle the DNA differently for each child.

Can you share DNA and not be related? ›

Yes, it is possible to share a small amount of DNA with someone and not be related. In other words, it's possible to share genetic material and not share a common ancestor or any identifiable genealogical connection.

Do half brothers and sisters share the same DNA? ›

The usual satisfying genetics answer right? It turns out that half-siblings share 25% of their DNA on average. But this is only an average. Because of how DNA is passed down from parents to children, some half-siblings will share more than 25% of their DNA and some will share less.

Why are children not identical copies of their parents? ›

Remember: everyone has two copies of every gene. Because we receive only half of our mother's genes (one copy of each gene) and half of our father's genes, we are not identical to either of our parents. With each pregnancy, the chromosomes from our mother and father combine in different ways.

Why do children get mixed characters from the parents? ›

Each parent gives half of their genetic material to their children. The combination makes a unique combination of their parents genes. The scientific study of how traits are passed from parents to children is called 'genetics'.

Why do siblings resemble with each other why mother and daughter look alike? ›

Answer and Explanation:

The siblings look alike even though they have the same biological parents, and this is due to DNA or genetic trait received from their parents. Each child receives 50% of DNA from their father and 50% of DNA from their mother. One gene is dominant, and the other is recessive.

Do Irish twins have a special connection? ›

Do Irish twins have a special connection? Irish twins share a strong bonding. They have an unbreakable friendship since they tend to do everything together and even share everything.

Why are twins always together? ›

Identical twins share a particularly intense bond. They are the result of one fertilized egg splitting into two, giving them identical DNA. (Fraternal twins are the result of two separate, genetically different fertilized eggs.) As a result, identical twins are as close as two people can be.

Why do twins have the same dreams? ›

In the case of twins, similar genes produce similar brains, which in turn process similar thoughts, feelings and sometimes even similar dreams at night.

Why do some siblings look nothing alike? ›

But brothers and sisters don't look exactly alike because everyone (including parents) actually has two copies of most of their genes. And these copies can be different. Parents pass one of their two copies of each of their genes to their kids. Which copy a child gets is totally random.

Is it possible to have a child that looks nothing like you? ›

Before you get paranoid that your child was switched at birth, it's best to understand that the culprit is most likely genetics. Although genetics has a hand in turning the baby into a mini-you, the same players also morph him into a mini-not-you.

Why do my kids not look like me? ›

You're not alone in wondering, why doesn't my baby look like me? Although there are many possibilities for the exact combination of genes your child could inherit, it all comes down to DNA. "Kids share 50 percent of their DNA with parents and siblings, so there's room for variation," reported Parents.

Why do siblings not inherit the exact same versions of every gene? ›

To do this genetic trimming, the chromosomes in cells line up in pairs and exchange bits of genetic material before forming an egg or sperm cell. Each mature egg and sperm then has its own specific combination of genes—which means offspring will inherit a slightly different set of DNA from each parent.

Why do siblings share half their genes? ›

But for reasons we will talk about in a bit, it turns out we are all pretty much 50% related to our brothers and sisters too. Both of these are true because of how DNA is passed from one generation to the next. We get half our DNA from our moms and half from our dads.

What traits do siblings share? ›

Siblings Close In Age May Not Share Toys Well, But They Often Share These 5 Traits
  • Mannerisms. So many moms may notice their little ones mimicking each other's mannerisms. ...
  • Sense Of Humor. ...
  • Academic Achievement. ...
  • They May Both Be Opinionated. ...
  • Shared Interests.
25 Jun 2019

Why do siblings with each other why mother and daughter look alike? ›

Answer and Explanation:

The siblings look alike even though they have the same biological parents, and this is due to DNA or genetic trait received from their parents. Each child receives 50% of DNA from their father and 50% of DNA from their mother. One gene is dominant, and the other is recessive.

Who is your closest blood relative? ›

List of who your nearest relative is
  • Husband, wife or civil partner (including cohabitee for more than 6 months).
  • Son or daughter.
  • Father or mother (an unmarried father must have parental responsibility in order to be nearest relative)
  • Brother or sister.
  • Grandparent.
  • Grandchild.
  • Uncle or aunt.
  • Nephew or niece.

Can Full siblings share 25% DNA? ›

On average full siblings will share about 50% of their DNA, while half siblings will share about 25% of their DNA. The actual amount may vary slightly since recombination will shuffle the DNA differently for each child.

Can you share DNA and not be related? ›

Yes, it is possible to share a small amount of DNA with someone and not be related. In other words, it's possible to share genetic material and not share a common ancestor or any identifiable genealogical connection.

Are you 100% related to your sibling? ›

However, there's an important distinction -- while everyone shares exactly 50% of their DNA with each parent, we share on average 50% of our DNA with our siblings. You can actually be slightly more or less than 50% related to a sibling, for reasons that are explained below.

Can a 1st cousin be a half sibling? ›

It's common for people to have half-siblings since not all children share the same two parents. When you take the Ancestry DNA test, since half-siblings only share 25% of their DNA, they may be categorized as your first cousin.

Why are you 50% related to your sibling? ›

Sibling relatedness

The 50% refers collectively to how much “genetic material” you get from each parent. You get 50% of your genes from your mom and 50% of your genes from your dad. You have two copies of each gene -- one copy from each parent.

How being an only child affects personality? ›

Also, lack of interaction with a sibling is believed to cause loneliness and antisocial tendencies. Some even think these effects carry into adulthood, with only children having difficulty getting along with co-workers, displaying hypersensitivity to criticism as they become older, and having poor social skills.

How Being the youngest child affects personality? ›

The Youngest Child - “The Baby”

Just as with the oldest sibling, the youngest child often feels special and has a unique place in the family. They tend to be more rebellious and attention seeking, creative, social, and outgoing.

What determines personality type? ›

Scientists estimate that 20 to 60 percent of temperament is determined by genetics. Temperament, however, does not have a clear pattern of inheritance and there are not specific genes that confer specific temperamental traits.

Do children look more like mom or dad? ›

However, several studies since then have shown that most infants resemble both parents equally. One study even suggests that in the first three days of life, the baby looks more like the mother—but she will tend to say the opposite, emphasizing the child's resemblance to the father.

Can a child look nothing like either parent? ›

Even though we get all our DNA from our parents, each of us has a unique combination of genes. Sometimes that means we don't look like them at all. There are tons of genes that shape our appearance.

Can a child look exactly like one parent? ›

Sometimes a child will look slightly more like one parent than the other, while sometimes they seem to morph from one to the other in an uncanny resemblance. Then you have children who are a striking resemblance to one parent and literally show no similarities to the other.

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