Surprising Facts About Siblings

Calling all parents of two or more — or simply those planning to have more than one: While it turns out the notion that birth order determines our personalities isn’t as scientifically sound as was once thought, there is lots of intriguing research about brothers and sisters you’ll probably find insightful or at least interesting.

Here, a few top sib tidbits.

Siblings spend more time with each other than with anyone else.

According to one study, by the time kids with siblings are 11 years old, they’ve spent roughly 33 percent of their free time with them. Even as they get older and have more outside interests and obligations, children still spend at least 10 hours a week with their brothers and sisters — in large families that number is more like 17 hours a week.

Siblings have a huge influence on our outlook, personalities and behavior.

That’s even more so than our parents (who have less effect on whether a child smokes or drinks, for example, than a sibling does). Eighty percent of us spend at least a third of our lives with a sibling or siblings, according to some research. Some research shows it may even lead to less depression, more life satisfaction and more self-esteem.

Siblings tend to resemble each other in looks but not necessarily in personality.

Despite sharing the same parents and upbringing, brothers and sisters are often quite different when it comes to their personalities. Why this is the case isn’t clear, though siblings do tend to try to differentiate themselves from each other.

Older siblings might be smarter.

Although there’s debate as to the significance, there seems to be a tiny difference. Several theories have been put forward, the most persuasive being that older siblings spend time teaching their younger siblings, thereby reinforcing their own understanding of concepts. It may also be that firstborns have a leg up because they had more of their parents' attention and enrichment opportunities before the baby came along.

Younger siblings may be less risk-averse and more extroverted.

Again, take this with a grain of salt. But if you believe at least some of the research, the runts of the litter tend to be more outgoing and bigger risk-takers. Some believe that this is because the littlest family members are forced to speak up and take risks in order to get attention (especially in large families).

And younger siblings tend to have fewer allergies.

Younger siblings may be slightly less likely to develop allergies and eczema than their older siblings, perhaps because by the time they arrive there are plenty of germs in the home environment thanks to older siblings. And germs, in turn, can help to build a stronger immune system.

Siblings may keep weight in check.

One study found risk of obesity drops by 14 percent for every additional sibling in a household, at least among daughters. Perhaps this is because siblings tend to keep each other physically active.

The more siblings you have, the less likely you are to divorce as an adult.

For every sibling someone has, their odds of divorce falls by 2 percent, at least according to one study. More siblings can mean more experience dealing with others — and that might create an advantage when it comes to negotiating the ups and downs of marriage.