In partnership with
Hey, Raising Humans Crew!
Picture this:
Two kids in the backseat: One has a bag of cookies. The other does not.
What happens in the next 90 seconds will teach both of them more about negotiation, fairness, empathy, and patience than almost anything you could sit down and intentionally instruct.
That is the sibling effect in action.
Whether your kids wrestle over the remote, form an impenetrable alliance against bedtime, or occasionally say things to each other that make your jaw drop, something remarkable is happening beneath the surface. Brothers and sisters are each other's first peer relationship, and that relationship does things for their social and emotional development that, quite honestly, parents simply cannot replicate on their own.
This week, we are diving into the surprising science of sibling dynamics, what kids are actually learning from those daily squabbles and moments of closeness, and how parents can harness that power rather than just referee it.
Plus, we have some ideas for parents of only children too, because the lessons here absolutely apply beyond the sibling relationship.
Let's get into it.
Also in this edition:
🧠 The Think Tank: Cast your vote in this week’s poll!
How Sibling Relationships Quietly Shape Life Skills
A study published in Child Development by researchers at the University of Toronto and University of Calgary tracked families with young children and discovered something striking:
Siblings as young as 18 months were shaping each other's empathy development in ways that went beyond what parenting alone could explain.
The research found that both younger and older siblings uniquely predicted increases in the other's empathic concern over time.
Not through direct instruction. Not through parenting.
Through each other.
Why does this happen?
Because the sibling relationship has a quality that the parent-child relationship, by its very nature, cannot have: equality of stakes.
When your child negotiates with you, the power dynamic is clear. You are the adult. You set the rules. Even when you are wonderfully collaborative and warm, your child knows on some level that you hold the cards.
But when they negotiate with a sibling? Both kids have skin in the game. Neither one automatically wins. Neither one can just opt out. And the relationship itself matters to both of them, which means they have a real incentive to work things out.
Researchers call this the "practice field" of social development.
Here is a quick breakdown of what kids are building through everyday sibling interaction:
Conflict Resolution
When siblings fight over something and eventually work it out (without a parent stepping in), they are practicing one of the most in-demand adult skills on the planet. They are learning to read someone else's emotions, advocate for their own needs, propose solutions, and tolerate when things don't go their way. This is not chaos. This is curriculum.
Perspective-Taking
Siblings are the first people in a child's life who regularly challenge their point of view from a position of equal footing. Unlike a peer at school who might just walk away, a sibling has to keep living with you. That shared life forces kids to develop a more nuanced understanding of how other people think and feel.
Emotional Regulation
Living with someone who knows exactly how to push your buttons, and caring deeply about them anyway, is an intense emotional workout. Children with siblings get dramatically more practice at managing frustration, jealousy, and disappointment in emotionally charged situations than children who spend most of their time with adults.
Loyalty and Trust
Sibling relationships introduce kids to a kind of bond that is chosen not because it is convenient but because it is family. Research shows that children who feel a strong sense of loyalty to their siblings develop more secure peer relationships in adolescence and greater psychological resilience overall.
The keyword in all of this is "warm." Cold or hostile sibling relationships do not produce these benefits; they actually produce the opposite. The goal for parents is not to force sibling harmony, but to nurture the conditions for genuine closeness.
Smart starts here.
You don't have to read everything — just the right thing. 1440's daily newsletter distills the day's biggest stories from 100+ sources into one quick, 5-minute read. It's the fastest way to stay sharp, sound informed, and actually understand what's happening in the world. Join 4.5 million readers who start their day the smart way.
Why Always Jumping In to Settle Sibling Conflict Might Hold Your Kids Back
Here is an uncomfortable truth that much parenting research points to: the instinct to immediately resolve sibling conflict might be one of the most well-intentioned things parents do… but it quietly undermines their children's development.
We get it.
The noise is relentless. Someone is crying. Someone is clearly wrong. You have a hundred other things to do, and this argument about who had the blue cup first is genuinely maddening.
Of course you want to step in.
But here is what happens when you do: you rob both kids of the most valuable part of the conflict, which is figuring out how to end it themselves.
University of Illinois researcher Laurie Kramer has spent decades studying sibling relationships, and one of her consistent findings is that the type of parental intervention matters enormously.
Her 1999 study in Child Development found that it depends on your kids' ages.
For older children, parents who jumped in every time a conflict started actually ended up with siblings who felt less close to each other over time.
For younger children, doing nothing at all tended to let things spiral.
The takeaway: there is no one-size-fits-all answer, but always playing referee is rarely the right move at any age.
More importantly, when a parent steps in and assigns fault, they short-circuit the emotional processing that makes conflict actually educational. The moment of frustration, negotiation, compromise, and reconnection is where the learning lives.
So what do you do instead?
The research-backed answer is not "do nothing."
It is "do less, but do it differently."
The 3-Step Low-Intervention Approach
1. Wait a beat. Give the conflict 60 to 90 seconds to breathe before you intervene. You might be surprised how often it resolves itself.
2. Coach from the sidelines rather than rule from above. Instead of deciding who is right, ask: "What does each of you need right now?" or "What would feel fair to both of you?"
3. Intervene for safety, not for comfort. Physical aggression or emotional cruelty requires immediate adult response. Ordinary disagreement and frustration? That is the good stuff. Let them practice.
One more thing worth noting: the sibling who is older or bigger will often "win" low-intervention conflicts… simply by virtue of power.
Part of healthy parenting is making sure the playing field is reasonably fair, and that younger or more introverted kids are not being consistently steamrolled.
You are not the referee. But you are still the coach.
What Only Children Miss Out On, and How to Fill the Gap Intentionally
About 20% of American children are only children, and that number has been rising steadily for decades. Only children consistently perform well academically, show strong self-reliance, and often develop deep and sophisticated relationships with adults.
But there is one area where the research does show a meaningful gap: the kind of spontaneous, daily peer practice that siblings provide.
Not because only children are less capable, but because they simply get fewer reps! There are specific skills that come from navigating an equal-status ongoing relationship with someone you did not choose and cannot leave.
The good news is that this is very much a fillable gap.
It just requires intentionality.
What to look for in peer experiences for only children:
Not all peer time is created equal. A playdate at the park where kids play side by side is fine, but it does not replicate the intensity of sibling dynamics.
What you are looking for are peer relationships with three qualities:
Ongoing and repeated. A weekly playdate with the same child builds a real relationship with real history. One-off interactions build surface-level social comfort, but not the deep negotiation skills that siblings develop.
Unstructured enough to generate conflict. Structured activities like classes or sports are wonderful, but they have rules that manage most of the friction. True peer skill-building happens in the unstructured in-between moments.
Close enough in age to feel like equal footing. Age-mixed friendships are great, but for developing the specific skills that siblings build, a peer relationship in which neither child has a clear authority advantage is most valuable.
Cousins, neighbor kids, consistent friend groups, and shared-room summer programs are all excellent options. The goal is to find what researchers call a "sibling-equivalent relationship," a bond that has enough longevity, stakes, and equality to generate genuine practice.
A Note for All Parents:
Whether your household has one child or five, the bigger message here is the same.
The peer relationships your kids build in childhood, the ones where they have to show up again and again for someone who is not going anywhere, are doing developmental work that no curriculum, tutor, or parenting book can do alone.
Your job is to protect the time and space for those relationships to deepen, and to resist the urge to smooth over every bump in them.
We’re asking parents like you to share their thoughts on topics that matter each week! Cast your vote and see what others think! We’ll chat more about the results next week. 👀
When your kids argue with each other, what is your default response?
Why We're Asking
Sibling conflict style is one of the most telling windows into family dynamics, and there is no shame in any of these answers. We are curious where you land and what you have tried.
This week's toolbox is focused on building the social-emotional skills that sibling dynamics develop, whether your home has multiple kids or one. These resources are parent-tested and research-grounded.
"Siblings Without Rivalry" by Adele Faber and Elaine Mazlish (Book): The gold standard for parents navigating sibling dynamics. Practical, warm, and grounded in real family experience. Even if you have read it before, it is worth a revisit through the lens of this week's research on sibling conflict as a learning tool.
Smiling Mind (app): A completely free mindfulness program for kids, teens, and adults with guided meditations tailored to different age groups.
"The Whole-Brain Child" by Daniel J. Siegel and Tina Payne Bryson (Book): Chapter 5 digs into how children develop the ability to connect with other minds, and it is directly applicable to the sibling skill-building research. The strategies for helping kids "name it to tame it" in conflict situations are gold.
Big Life Journal's Sibling Activity Pack (Printable): A beautifully designed set of conversation prompts and shared activities specifically designed to build sibling bonds. Great for car rides, family nights, or rainy afternoons. Easily adaptable for close friends if you have an only child.
Thinkster Math (App): A small plug for our own program this week, because it fits. One of the underrated features of Thinkster is that kids often want to challenge siblings or friends to beat their scores and track their streaks. Healthy competition with someone you love? That is the sibling effect at work.
Until Next Week…
The sibling relationship, or the sibling-equivalent relationship for only children, is one of the most powerful developmental engines in a child's life.
And the most important thing parents can do is often the hardest: get out of the way a little, trust that the friction has a purpose, and stay warm and present without trying to manage every moment of it.
The kids who argue loudest in the backseat today are building the conflict resolution, empathy, and loyalty skills they will lean on for the rest of their lives. That is worth a lot more than a quiet car ride.
Thanks for joining us in raising kind, capable, and confident humans. We’re so glad you’re here.
❤️ Loved this issue? Have thoughts, questions, or topic ideas?
Share your vote below or drop us a note at [email protected].