Age Gaps Between Siblings Are Widening—and It’s Shifting the Birth Order Dynamics

Ever since I became pregnant with my second child—a boy!—there’s been one single detail I’ve been stuck on: The age gap. My first-born will be six years older than my newborn, something that feels lightyears ahead in terms of development. Will they still squabble over toys? Fight for their parents attention? Enjoy a rich bond? These are just a few of the worries questions bouncing around my head.

That’s when I came across some recent and surprising research: Broader age spacing between siblings is becoming more common, according to a 2020 study that analyzed modern day fertility. This, in turn, may be altering family (and birth order) dynamics—and not in a bad way.

First, a quick look at the data: Between 1967 and 2017, the spacing between sibling births only increased by a minuscule amount—about three quarters of a year. Compare that to now when 22 percent of moms space their kids out by six or more years, per the study. Research shows that siblings are still—on average—about four years apart, but present-day fertility resources (not to mention an evolving definition of the American family since the 1960s) is leading to a more rapid expansion of that gap.

For example, couples who want to have kids now have access to contraception (meaning they have more control when it comes to planning their pregnancies); there’s also services like IVF, which can help extend the childbearing window in addition to augmenting a difficult fertility journey. Add to that changing family dynamics. Life experiences like divorce and remarriage (also known as multi-partner fertility) are other factors that can also cause a wider sibling age gap.

On top of all this, the modern fertility rate is dropping and for a variety of reasons—women are waiting until later to have kids and electing to have fewer of them, too. (Insert tangent here about the lack of support for working parents.) Regardless of the reason, if you’re not planning to pump out five babies, that’s another factor that lessens the rush to have them one after the other.

But now the bigger question, which goes back to my original concern: If age gaps are widening, how will that impact sibling relationships and kid’s personalities in the future?

To find out, I consulted Dr. Laurie Kramer, a licensed clinical psychologist and professor of applied psychology at Northeastern University, where she leads the Siblings Research Group. (She’s also the founding director of the Family Resiliency Center at the University of Illinois.)

She explains that it really comes down to parental resources. “Think about a 6-year-old who’s becoming a sibling for the first time, and they’ve had six years of undivided attention from their parents, grandparents and more. When they were first born, parents are also excited and attentive and working hard to try to understand and meet the needs of this child. With only one, they have the luxury to do that.” Add one sibling—or four—and everything changes, Dr. Kramer continues. In other words, attention gets divided.

But a broader age gap has the potential to soften that blow. Wider spacing means parents likely have more availability—everything from time to patience to money. Yes, that massive change to a family dynamic is hard, but it’s happening alongside an older kiddo who probably already has developed a whole host of social and emotional competencies, which Dr. Kramer says are critical when it comes to forming a positive bond with another child, especially a sibling. “Parents with kids that have a larger age gap can capitalize on that developmental maturity, which will ultimately really help the child be able to cognitively grasp what’s going on.” (Saying something like, ‘We’re having another child, this is so great, we’re still going to love you,’ will be more easily processed by, say, a 6-year-old than a toddler.)

This means there’s a greater likelihood of what Dr. Kramer calls perspective-taking. “The older child may be more astute when it comes to trying to interpret a new baby’s wants or needs,” she explains. “And if they’re feeling suspicious around things like, ‘How are my parents going to continue to meet my needs while doing the same for this new baby?’ they’ll have the cognitive and linguistic skills to share their emotions in a way that’s accurate vs. irrational.” In other words, less tantrums, more talking—all of which can enhance the budding relationship between brother and sister.

That doesn’t mean there won’t be unique challenges, too. A larger age gap likely means divergent interests and for parents in need of time-saving opportunities (say, a shared after-school activity), a wider age gap means that won’t align. It may also be less of a disruptive life change for an older child who is able to carry on their normal, typical activities—things like school and friendships outside the family—but it also could lessen the connection between that older child and the baby.

Does this mean birth order theories (things like eldest daughter syndrome or the youngest being a risk taker) no longer apply? Dr. Kramer is clear that this is a recent trend and one where the long-term impact is still being studied. But it certainly has the propensity to upend what we know.

Dr. Kramer says the people who are truly in the driver’s seat when it comes to sibling dynamics and outcomes are—surprise—the parents. “The number-one question parents need to ask themselves when raising siblings is, ‘What’s the kind of relationship I want my kids to have with one another?’” she says. The larger the age spacing, the more effort it takes to bridge the gap. “Again, parents with an older child have an advantage in that they can really talk to their older child and be more sensitive to their needs and have bigger discussions.” They can nurture and structure the connection versus constantly operating from a place of putting out fires (things like refereeing squabbles and more). But extra effort will need to be made to point out commonalities and help kids find shared interests and ideas, she adds.

No pressure, mom and dad.