What we learn from our siblings when we grow up has — for better or for worse — a considerable influence on our social and emotional development as adults. According to Laurie Kramer, expert in sibling, parent-child and peer relationships at the University of Illinois, our parents’ influence on our development as children shouldn’t be underestimated, but neither should a sibling’s.

“What we learn from our parents may overlap quite a bit with what we learn from our siblings, but there may be some areas in which they differ significantly,” Kramer said to Science Daily.”Siblings are closer to the social environments that children find themselves in during the majority of their day, which is why it’s important not to overlook the contributions that they make on who we end up being.”

While parents are better role models for more formal settings, such as how to act in public and other social and moral norms; siblings help with more informal behaviors, like how to act at school or how to be cool around friends.

It has long been assumed that the birth order of siblings affects their personalities, and this study by British researchers YouGov seems to confirm this.

“Splitting out the first and last born siblings in British families with more than one child (86% of the population), a clear divide in personality traits emerges,” they write. “The most significant difference is in feeling the burden of responsibility – most (54%) first borns say they are more responsible than their siblings, compared to 31% of last borns.”

“Younger siblings, on the other hand, are more likely to say they are more funny (46% compared to 36% of elder siblings), more easy going and more relaxed.”

Having a sibling might even be good for your overall health, even if it doesn’t really feel like it when you’re a kid. Because according to one study, becoming a big brother or big sister before first grade may lower a child’s risk of becoming obese. The study, led by the University Of Michigan, found that children the same age who didn’t have a sibling were nearly three times more likely to be obese by first grade.

“Research suggests that having younger siblings — compared with having older or no siblings — is associated with a lower risk of being overweight. However, we have very little information about how the birth of a sibling may shape obesity risk during childhood,” senior author Julie Lumeng, M.D., a developmental and behavioral pediatrician at U-M’s C.S. Mott Children’s Hospital told Science Daily.

“This study is believed to be the first to track subsequent increases in BMI after a child becomes a big brother or sister.”

One possible explanation, the authors speculate, could be that parents may change the way they feed their child once a new sibling is born. With children developing long-lasting eating habits at around three years old, changing dietary habits may have a significant impact.

Authors also note that children may engage in more ‘active play’ or less sedentary time in front of screens once a younger sibling is born, contributing to healthier BMIs.