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35 Birth Order Facts & Statistics: Fact or Fiction?

Does birth order matter? Let's explore how it impacts child development.

There are many famous stereotypes about birthing order. For example, the oldest child might be a natural-born leader; the middle child is often referred to as wild; the youngest child is known to be the doted-upon baby. But how accurate are these cliches?

I’ve delved deep into official research and studies to uncover the truth about the effects of birth order. We’ll discuss 35 interesting birth order facts and statistics about first-borns, middle-child traits, and last-born characteristics. And don’t worry, we’ve not forgotten about only children! I have seven astounding facts about their personality traits, too.

So, let’s investigate whether birth order concepts hold water or if they can’t withstand proper analysis.

Key Facts About Birth Order

Let’s look at the 10 most interesting facts about birth order from this article:

  1. First-born children have better academic success and are more likely to become leaders.
  2. Firstborns are more fearful of physical injury and the idea of pain than younger siblings.
  3. Middle-born children in the U.S. are reported to have the lowest self-esteem, especially males.
  4. Middle-born children are more likely to engage in substance use by 33 percent.
  5. Last-born children are the least likely to experience mental health challenges.
  6. Out of all siblings, the youngest child is more likely to be the least intelligent.
  7. Only children (and last-born children) are the happiest of the birth order.
  8. Only children are more ambitious than middle-born or last-born children from other families.
  9. Children born last typically have lower IQs, but birth order is not as relevant as family size. For example, last-born children of larger families have a lower IQ than last-born children of smaller families.
  10. As a last-born child, Cara Delevigne might be assumed to be less mentally fit and earning less money. But she doesn’t typically fit into this role, as she is wealthy and has mental health challenges.

What is the Birth Order Theory?

Birth order theory is a well-known hypothesis put forward by Alfred Adler, an Austrian doctor and psychotherapist. His theory speculated about how birth order might affect children, both positively and negatively (1).

He concluded that children within the same family have different life experiences and outcomes based on whether they were born first, in the middle, last, as a twin, or an only child.

To summarize his theory, below is the hypothesis he had for each type of child:

  • Only children: Only children get more attention and, therefore, enjoy being the center of adult attention. Only children typically enjoy adult company and often use adult language, but they may also become the rivals of one parent. They might have difficulty sharing, and they can be overprotected and sometimes spoiled.
  • Oldest children: Oldest siblings are ‘dethroned’ when their sibling comes along, so they are forced to learn to share. They are also forced into being a role model for their younger siblings. Parents usually have high expectations for their oldest child. In return, the oldest children might be stricter and crave control.
  • Second children: Second children become the peacemakers as there is always someone ahead to keep an eye on. However, they also are more competitive as they try to outdo their older sibling. This can turn into sibling rivalry.
  • Middle children: Middle children might feel left out and insignificant. They have to adopt an ‘it is what it is’ attitude. They might feel like an outcast, which can lead to becoming an advocate for injustice.
  • Youngest child: The youngest child has many parental figures to look up to, including both parents and older siblings. They are never dethroned from their position, which ensures they are the ‘baby’ of the family forever. However, the youngest child wishes for more authority or to be seen as older than they are treated. They are often dreamers, sometimes perceived as less goal-oriented. They are also spoiled as if they were an only child.
  • Twin children: As a twin, one child is usually stronger or more active than the other. One of them is usually treated as the ‘older’ sibling. Twins can have struggles with their identity.

Adler’s birth order theory, developed as part of his broader psychological work in the early 20th century, served as a framework to better understand personality traits. Initially proposed as a theoretical concept, it has since been the focus of numerous official experiments, tests, and research efforts, all aimed at exploring its validity and implications.

35 Interesting Facts About a Child’s Birth Order

Below are 35 interesting facts about birth order. You’ll find seven facts across five categories: first-born children, middle children, last-born children, only children, and examples of birth order traits.

First-Born Child Characteristics

Does being first-born mean that you will be controlling, structured, and reliable, as the stereotype suggests? Here are seven amazing facts about how birth order affects first-born children.

  1. First-borns have better academic success: A survey of over 200 birth order studies found that first-born children perform better academically (2). They have a higher chance of becoming leaders.
  2. First-borns are less likely to use substances: A study found that being first-born males and females was the most protective factor against using substances (3). These people were less likely to use drugs and alcohol.
  3. First-born children get more attention: Not only do first-born children get more attention from their parents, but they are also more likely to get financial support. This money is often used towards one’s education, which gives them a higher chance at exceeding in their career and becoming leaders.
  4. Firstborns are more fearful: Studies suggest that firstborns are more likely to avoid dangerous sports due to a fear of physical injury (4). Firstborns typically find the idea of pain to be scarier than their younger siblings would. In an experiment that involved tolerating an electric shock, first-born girls were more scared and less tolerant than later-born girls.
  5. First-born children have a higher ego: A study found that first-born children are likelier to have a superego (5).
  6. First-borns have a higher IQ: Studies have found that first-born children have a slightly higher IQ than later-born children (6). Thus, they typically get a higher degree and choose more prestigious careers, like engineering. They are also more likely to work as managers in jobs that require sociability, agreeableness, and emotional stability (7).
  7. First-born children are more likely to be overweight: First-born children are four percent more likely to be overweight than their next-born sibling. They are two percent more likely to be obese. If they are the oldest of five siblings, they are 10 percent more likely to be overweight. They are also more likely to have high blood pressure.

Middle Child Traits

Let’s glimpse into the research surrounding middle children and their personality traits, characteristics, and how they might fare in the big bad world.

  1. Middle children develop quicker: Second or middle children often hit their milestones quicker. This is because they have an older sibling to look up to and be compared against. Thus, they are geared towards competing against their older sibling and matching their pace while ensuring they outrun the youngest singling.
  2. Middle-born males and low self-esteem: Studies in the US have found that middle-born male children have the lowest self-esteem (8). Research has also found that middle children, both male and female, are less happy than children of other birth orders, especially last-born or only children. This may be due to a ‘lack of uniqueness’ in the family. They don’t have as much reason to receive attention from their parents as first or last-born children do.
  3. Middle children are more likely to become delinquents: Studies found that middle children are more likely to have issues with delinquency in order to gain attention (9). Because of a lack of parental attention, middle-born children may seek attention from their peer group, which can easily lead to delinquency.
  4. Middle children are more likely to use substances: Middle-born children are more likely to engage in substance use and other risky adolescent activities, including sex. Overall, middleborns were 33 percent more likely to display problem behaviors than first-borns.
  5. Middle children become peacemakers: Middle children naturally become peacemakers in their families (10). Since they’re sandwiched between older and younger siblings, as well as competing for attention, they often become peacemakers.
  6. Middle-child syndrome isn’t officially recognized: While there are many studies to reveal the adverse effects of being a middle child, it’s not a recognized syndrome (11). It’s more a hypothesis at the moment and, in many cases, a way to poke fun at families. So, even though there is evidence to show how rough being a middle child is, it’s important to note that many of these studies don’t consider family size and parental support.
  7. Middle children may go extinct: Okay, I’m being a little dramatic here. However, the average family size has gone from 3.67 people to 3.13 since 1960 (12). With more people having fewer kids and often completing their family with just one or two children, middle children may be no more!

Last-Born Child Characteristics

Birth order data is absolutely fascinating. If you want to know more about last-born personality types and characteristics, check out these seven noteworthy facts.

  1. Last-borns are least likely to have mental health challenges: Last-born children are less likely to experience mental health challenges. This may be because older siblings can mitigate the risk of mental health issues. Last-borns receive emotional support from older siblings, which offers a sense of security.
  2. Last-borns are more prosocial: Last-borns are more likely to have prosocial traits, including resilience. In theory, this could be because they have more interactions with older children, which allows them to develop their social and emotional behaviors in a more controlled environment. They spend more time with their siblings than their parents, allowing them to understand other people’s emotions and intentions while cultivating problem-solving skills.
  3. Last-born children earn less: Children born last are more likely to earn less money and not work full-time (13). This is especially true for women. Male last-borns are more likely to have lower wages, but they are not less likely to work full-time. There is quite a stark difference in educational attainment between first-born children and last-born children, especially in larger families.
  4. Youngest children are the least intelligent: Out of the siblings, the youngest child is more likely to be the least intelligent ( source). Studies have found that intelligence decreases gradually with each child. This may be due to each child born getting less parental attention, higher expectations on the older children, or parents expecting older children to tutor their younger siblings.
  5. Youngest siblings have more chill: According to a 2015 survey, youngest siblings were more likely to be laid back (14). Forty-six percent said they were the ‘funny sibling’ compared to 36 percent of older siblings. Forty-seven percent said they were more easygoing, compared to 42 percent of older siblings. Forty-two percent said they were more relaxed, compared to 39 percent of older siblings.
  6. Last-borns are more likely to change their views: Youngest siblings are more likely to change their political, social, or scientific opinions during times of radical change (15). Research has found this is due to the youngest siblings being more socially liberal; when radical reformations come about, this taps into their nonconformist traits. For example, in Catholic countries, last-borns were nine times more likely to die for the Protestant Reformation rebellion than first-born children (16).
  7. Last-borns use low-power strategies: When trying to get what they want, last-borns use lower-power strategies instead of aggression and intimidation. This includes whining, humor, and appealing to their parents. This is typically because they are smaller than their older siblings. Another interesting fact is that older parents will typically ‘invest’ in their last-borns since they are more vulnerable to disease and the babies of the family.

Only Child Personality Traits

I’ve touched on how sibling order may affect a child’s personality traits. But what about child development and personality types for only children? How does being an only child affect their psychology? Let’s look at what the research has to say.

  1. Female-only children are more likely to take substances: Female-only children are more likely to consume alcohol, tobacco, or marijuana than male-only children. Both genders are more likely to consume substances compared to first-born children.
  2. Only children are happier than first-born and middle-born: Studies have found that only children (and last-born children) are reported as being happier than first- or middle-born children.
  3. Only children are more ambitious: Only children are more ambitious than middle-born or last-born children from other families. They are also more likely to conform to their parent’s rules. There is also a stereotype that only children aren’t as sociable, but studies have disproved this.
  4. Only children are more likely to have anxiety: Only children have been found to be more anxious compared to first-, middle-, and last-born children (17). Tests found that only children were significantly more likely to experience anxiety, depression, or both (18). However, there are other factors at play, including their relationship with their parents, how much sleep they get, their eating habits, and their academic success, which can also affect their susceptibility to anxiety.
  5. Extra parental attention may be positive: Only children often get a bad rep for being spoiled or poorly adjusted. However, some research has found that this extra parental attention can have positive effects (19). For example, only children have higher IQs than later-born children. They also have more secure attention and a lower need for social affiliation, possibly because they receive it from their parents.
  6. Only children have better relationships with parents: A study found that only children often had more positive relationships with their parents than children with siblings (20). This positive relationship can significantly affect a child’s development, intelligence, and success. Another study found that 25 percent of only children described their relationship with their parents as positive (21). This is compared to only 18 percent of last-born children.
  7. Only children often regret not having siblings: A 2001 study found that many only children were regretful about not having siblings. In fact, research found that only children were more likely to have imaginary friends during preschool years compared to children with siblings.

Birth Order Examples

Now that you know amazing facts and statistics about birth order theory, are you curious about birth order examples?

I’ve put together examples of real people and families, including celebrities and historical figures, who have reported their birth order findings. I’ve also included some hypothetical or more abstract examples to give you an idea of how birth order functions.

  1. Astronauts are more likely to be first-born children (22): There is evidence that astronauts are more likely to be first-born. At first glance, we might assume that birth order theory is correct here. Perhaps first-born children are more likely to meet high expectations or become ‘role models’. But there’s also the possibility that astronauts come from smaller families, meaning they have a higher chance of being first-born (if they have none or one sibling). Smaller family size means the parents have more resources (money and time), which allows them to better invest in their child’s education. Therefore, if children had better education and parental support, they would likely become astronauts due to family size and privilege rather than just being born first.
  2. Birth order may be less relevant than family size: Children born last are found to typically have lower IQs. But as families have more children, the IQ of the last-born child decreases gradually. This implies that it has less to do with birth order and more to do with family size, fewer resources, and less parental support.
  3. Beyonce is a first-born: Beyonce is a great example to look at as a first-born child. She fits into the stereotype: she’s a perfectionist, a self-proclaimed ‘control freak’, and she has experienced anxiety and depression. Since first-borns are also likely to receive more attention, she falls into that category, too, as she has a huge audience of fans.
  4. Mark Zuckerberg is a middle child: Birth order theory would assume Mark Zuckerberg feels like an outsider and may adopt an ‘it is what it is’ attitude. Research shows that middle children develop quicker, often have lower self-esteem, and are more likely to become peacemakers. Mark Zuckerberg has reported feeling like an outcast, and he was already creating messaging programs at the age of 12 (23). He has also experienced self-doubt, which is traditionally associated with middle-born children (24). Zuckerberg has also done some work to fight injustice, which is also proven to be a middle-child personality trait (25).
  5. Cara Delevigne is the last-born: Cara Delevigne is the youngest of three children. Birth order theory could assume she is spoiled, the family ‘baby’, and more of a risk-taker. Research shows that last-born children are least likely to suffer mental illness, be more prosocial, and earn less money. Cara Delevigne doesn’t typically fall into the research or the stereotype. On one hand, she is definitely a risk-taker, especially in terms of her Met Gala outfits. But on the other hand, she is not a low-earner, and she makes more money than her siblings. She has also had a range of mental health challenges, including depression, anxiety, and substance abuse (26). So, in this case, birth order theory and research don’t apply as much to Delevigne.
  6. Adele is an only child: Let’s see if she fits the stereotype of being selfish, lonely, and independent and if she does what the research states. Female-only children are found to be more likely to take substances, be more ambitious, and have a good relationship with their parents. Well, Adele has a bit of a reputation for being selfish, especially since the release of her song ‘Go Easy On Me’. She also writes many songs about loneliness. Adele is also quite independent. While she is currently in a relationship, she went through a divorce in 2021. She also had a heavy smoking habit, which could link back to the research surrounding substance use. Adele is also very ambitious and has a great relationship with her mother.
  7. Celebrities who play into birth order theory: Let’s look at a few more celebrities who play into birth order theory. Hillary Clinton, J.K. Rowling, and Bruce Willis are all firstborn children. They are very ambitious and often more aggressive than middle or youngest children. Middle-children celebrities include Bill Gates and Princess Diana, who are more laid-back and often peacemakers. Last-born children include Jim Carrey, Eddie Murphy, and Cameron Diaz, who are all creative, charming, and sometimes manipulative.

Is Birth Order Theory True?

Birth order theory, a hypothesis put forward by an Austrian doctor, is also known as Adler’s theory. It hypothesizes that children have certain personality types depending on what order they were born into their family.

Firstborns are typically better role models, controlling, and often meet high expectations. Middle-born children can be competitive, feel like outsiders, and become advocates for injustice.

Last-born children often wish for more authority; they have dreams they cannot reach, and they may be spoiled. Only children have a reputation for being spoiled, enjoying adult company, and having difficulty sharing.

Research and studies have found some of this theory true, but some have been disproven or added to. For example, studies found older children to be more fearful, have higher IQs, and are more likely to be overweight.

Middle-born children have quicker development, lower self-esteem, and are more likely to use substances. Youngest children are less likely to have a mental illness, they are more likely to earn less money, and they are more laid-back than their older siblings.

Only children are more likely to take substances, they are more ambitious, and they are more likely to have anxiety.

So, while Adler’s birth order theory may not be 100 percent accurate, there is definitely research to suggest that birth order does affect a child’s personality.

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About the Author

Beth McCallum

Beth McCallum is a Scottish freelance writer & book blogger with a degree in creative writing, journalism and English literature. She is a mum to a young boy, and believes that it truly takes a village. When she’s not parenting, writing about parenting, or working, she can be found reading, working on her novel, taking photos, playing board games or wandering through the countryside with her family.