What your sibling birth order does — and doesn’t — explain

Even if you’re an only child, familial relationships do impact who you are: How your family of origin sees you, treats you, and interacts with you influences the way you think and move about the world, especially in your early years.

These forces come into play the moment you’re born. New parents are often highly motivated to anticipate and meet every whim of their firstborn, explains Laurie Kramer, a professor of applied psychology and the principal investigator of the Sibling Research Group at Northeastern University. Like teens taking their driver’s license exams, first-time parents are cautious, demonstrating extra care not to mess up their little human. This baby is born into an adult-centric world — adults whose primary goal is to care for this sole child’s needs.

Once second and subsequent babies enter the picture, parents are more relaxed in their child-rearing. They also have the added challenge of caring not only for a newborn but any other children — and helping their kids form relationships with one another. “Growing up in a household where there's already another child means that that second child or maybe that third or fourth child is growing up in a different kind of environment than that first child,” Kramer says. “So it's not so much the birth order as much as it is the way that the family relationship patterns are developed.”

Aside from greater exposure to adults, oldest children are often interested in or encouraged to pursue caregiving roles once younger siblings enter the picture. The move is doubly helpful to parents: They get an extra set of helping hands (crucial in single-parent households) and the setup allows their children to bond, Kramer says. As a result, the oldest kid may very well develop a sense of responsibility and leadership — qualities fostered through the environment rather than inborn traits. Amanda Evans, the oldest of four, traces her dependability back to childhood. Growing up, Evans helped her younger siblings with homework, organized games, and was the in-house babysitter. “I did take pride in helping out,” says Evans, now in her late 30s, “although I admit it was sometimes a hefty weight on young shoulders.”

With the role of “responsible one” already assigned, other children search for their place within the family dynamic. Younger kids may rebel against their older sibling’s model, thanks to a phenomenon called sibling deidentification, Kramer says. In order to establish themselves as unique individuals, younger siblings adopt the qualities they admire in their older siblings but forge their own interests. “When a younger child comes into the family and observes an older child being academically inclined, being more comfortable with adults, they may search out a different role for themselves because they want to be unique and have something different to present to the world,” Kramer says. “Those kids might decide, ‘Maybe I'm really good at sports or the arts. Or maybe I tell really funny jokes. I can be the social person.’” The more children there are, the fewer avenues they have to express their individuality, and they may gravitate to more mischievous behaviors, like getting into trouble at school. Sibling deidentification can play out in the inverse, too: Perhaps the oldest child develops a rebellious streak and their younger siblings are straight-laced, which directly plays against stereotypes.

But gender and cultural expectations, independent of birth order, can just as easily shape a child’s responsibilities and career prospects. A bulk of the caretaking or kinkeeping — the work of keeping a family together — falls to women, says Catherine Salmon, a professor of psychology at the University of Redlands. If an oldest daughter happens to have a younger brother, that split of gendered expectations is even stronger, research shows: Older daughters will take on more housework than their little brothers. Even younger sisters will do more housework than their older brothers, the study found. In patrilineal traditions — where names and property are passed down through males in the family — firstborn sons, even if they aren’t the oldest child, may be expected to take on more responsibilities, like carrying on the family business instead of going to college or pursuing a profession dictated by the parents, Salmon says. “In the royal family, Prince William has a different life than Prince Harry because that's what their culture decided,” says Rodica Damian, an associate professor of social and personality psychology at the University of Houston. These outcomes are predicated on external expectations rather than birth order alone.

Birth-order archetypes are so popular for a reason: Many people identify with them. These labels can stick into adulthood because the expectations foisted upon you as a child just so happen to fit your personality. A second-born child might be a great artist not because of birth order but because they had access to a great arts program that their older sibling didn’t. Just as easily, the oldest child may rebel against the pressure of setting a good example for their younger siblings.

There’s confirmation bias at play here, too. If you’ve been consistently told you’re the responsible one, or the athletic one, or the helpless one, it starts to become a part of your identity, Damian says. That can be hard to shake. These patterns are shortcuts for helping the family operate smoothly, Kramer says: expecting your older sister to make dinner reservations for a parent’s birthday, telling your younger sibling to plan your bachelor party. It’s easy to keep a familiar routine when you’ve done it for so long. “If someone falls into a particular role, they likely will maintain aspects of it at minimum for much of their life,” says Whiteman, the Utah State University professor. “But it's not a fait accompli.”

At 65 years old, Brian Jackson, the youngest of four boys, still feels like the spoiled little kid of his childhood. With eight years between him and his closest brother, Jackson was considerably younger than his siblings, who took on the bulk of chores and were held to stricter rules than he says he was. Jackson and his wife never had children “so once again, I never stepped into that role of having to take care of younger people,” he says. “I never had a desire to have children, and maybe that's because growing up I was never really around children. I never had to take care of younger siblings.”

It’s common to outgrow the part you were assigned in childhood. People who develop a strong sense of independence are more likely to break away from familial expectations if they don’t fit their desires, Salmon says. “If people are very confident in themselves, they're very confident in their relationships with their family, they're more likely to be willing to actually step outside that box and do what they think is best for them,” she says, “while still being able to maintain good relationships with the family.”

Amanda Evans, the oldest child who took on caretaking responsibilities with her siblings, established boundaries with her family so she didn’t default to the leadership role. For instance, Evans and her siblings have a divide-and-conquer mindset when it comes to helping out with their parents: One sibling handles tech issues, she says, and another is in charge of financial matters. Kramer suggests broaching these conversations with your own family if you’re beginning to feel resentful. An older sibling might say, “I've been the one to make plans for Mom's birthday every year. Who wants to do it next year? We can take turns planning. It doesn't always need to be my responsibility.”

Parents also have a say over how their children interact, and how they react to birth-order archetypes themselves. If parents of young children spot common birth-order characteristics, like their oldest daughter offering the bulk of caregiving support, they can encourage their other kids to reciprocate. “Even if they're younger, they still can be perfectly competent supporters of older siblings as well,” Kramer says. “When those things are more reciprocal, it feels more equal.” Stephanie Edenburgh, a 42-year-old mother to three sons, is deliberate in making sure her middle child feels loved and appreciated since she understands the pain of feeling overlooked as a middle child herself. “I try with my middle child to make sure he gets not extra attention, but I do try to give him a little bit extra,” she says, “because I feel like it's bound to happen where he's going to feel a little neglected.”

As children grow into adults, developmental and life milestones are natural turning points for change. The power imbalance between an oldest kid and their younger siblings evens out when everyone reaches adulthood. “An older sibling doesn't necessarily have more cognitive capacity or physical capacity at that point,” Whiteman says. “Transitions in life are when family system patterns change.” Whether your little sister has a child or your middle brother graduates from military basic training, these changes signal a sibling’s new roles: parent, a member of the armed forces, the responsible one, the strong one. How you relate to and view your siblings after these milestones will probably change.

Although you may always view your kid brother as, well, your kid brother, they aren’t the person they were in childhood. Neither are you. Birth order certainly impacts how everyone in the household relates to one another, but it isn’t who you’re destined to be.