The Sibling Effect: How Brothers and Sisters Quietly Shape Motivation, Confidence, and Identity
I have an older sister who is three years older than me, and I have a half sister who is seven years younger than me (but not raised with me and my older sister). My older sister was the golden child – the singer, the actor, the quiet one, the reader… I was the loud, noisy, active little sister who championed on her older sister who got to do some really cool stuff that admittedly was not my thing… but left me wondering, what was my thing? My claim to fame? My sister had singing until she burnt out. She had acting until she decided she wasn’t into that. I went to all the practices, all the performances, sat next to my grandmother who made her costumes. And I actually loved all the attention she got. It was amazing to see her up there feeling and looking confident. The downside was at home, when my mom would tell me how alike her and my sister were – they both loved books, were introverts, wore glasses. It left me feeling like an outsider when all I wanted was to be like my mom and sister. I can remember at young age thinking, when I have kids, I will make sure they know that I recognize the similarities we have because no one wants to be left out.
This is clearly a poignant memory for me, and any time I come across research or an article about siblings, I am so curious because of my older sister, and of course because of my own kids. We parent individuals – although siblings, they are raised by different parents. My son had a first time mom and dad, we didn’t know what we were doing. Although I can say I don’t know what Im necessarily doing with my daughter all the time, I had more experience under my belt. I recognize they don’t have the same experiences growing up. My daughter has only known a life with her big brother there. My son doesn’t necessarily remember the two years before his sister came along, but he knows there was a time it was just mommy, daddy, and him. And I would be remis if I didn’t mention that my daughter was born in the beginning of covid, so her first and really second year of life were NOTHING like his. So we parent individuals but we raise them in a system. And in that system, the quiet force we often underestimate is the sibling dynamic.
Susan Dominus’ 2025 New York Times Magazine article, “The Surprising Ways That Siblings Shape Our Lives,” brings long-overdue attention to this invisible but mighty force field: the way children are molded by their brothers and sisters, not just genetically, buy psychologically, socially, and emotionally.
We’ve focused on the parent-child bond as the primary engine of development. But the latest research shows that siblings act as co-architects of identity, role formation, self-esteem, and even academic outcomes.
Lets break down some overlooked truths about siblings and development:
1. Siblings are developmental architects. Kids aren’t just shaped by parents, they’re shaped by their environment and that environment is their sibling. They are shaped by the way they’re mirrored, contrasted, and compared to their sibling. These interactions become the scaffolding for motivation, risk-taking, and identity. They decide who gets to be the “smart one,” the creative one,” “the emotional one,” or even the favorite one, whether we admit it or not. How we label our kids and how they play into those labels not only affects the one labeled but the one not labeled as well.
2. Parental perception create long-term scripts. Even when siblings get similar grades or skills, research (McHale et al., 2015) shows that parental belief about who’s more capable can hardwire performance differences over time. The story we tell about our kids shapes the story they tell themselves.
3. Competition and comparison can mimic motivation but can hurt identity. What looks like ambition may actually be a survival strategy. Particularly in high-performing siblings, identity becomes reactive: success is less about passion and more about not disappearing because the other sibling sucks the life out of the room.
4. Birth order effects are real, but class and culture rewire them. In BIPOC families, multilingual, immigrant, or high-risk families, younger siblings often become leaders, translators, or protectors. Their roles reverse typical birth-order assumptions. (Lareau, 2011; Zang et al., 2022). I know this one all to well. No one calls my sister for help, its me. Its frustrating, I’d love for those roles to be reversed.
5. Spillover is powerful, for better or worse. A siblings success or struggle ripples through the entire family. Research by Zang and Goodman found that older sibling’s academic performance strongly influences the younger sibling’s outcomes, even when their paths seem unrelated. I feel this one heavily. My sister was a very artistic person who needed a less conventional school to offset her abilities. Whereas my traditional school was rigorous and I felt like I had to well to counter what my parents and grandparents thought schools should look and feel like.
What This Means for Parents
Parents, we must become aware of the invisible labels we reinforce: “she’s the shy one,” “he’s the go-getter,” “this one’s easy, that one’s tough.” These roles aren’t static, they are some times strategic. Kids choose them to survive family systems, and not be forgotten, left behind, or feel as though they don’t belong. Other times, its personality traits that don’t align with ours. This is no fault of theirs. If we want them to grow, we have to drop the scripts and parent the individual child in front of you.
Sibling dynamics can also shape stress regulations, perfectionism, and emotional avoidance. One child’s anxiety may actually reflect a siblings unspoken pressure or internalized shame. So its important to treat the system at home, not just the symptom by digging deep and question what is this behavior trying to show me about my child? And are we perpetuating a label or rewiring an internal narrative?
The “sibling effect” also shows up in the classroom as shadow behavior: one child shrinks because their older sibling “already did it best.” Or younger siblings may over compensate to make up for an older siblings shortcomings or struggles. Awareness of family roles in the classroom can shift how teachers also support self-efficacy and engagement especially if they have the same set of teachers.
So what can we do?
- Use inclusive language like “you both each bring something different to this family,” instead of labeling one child something and their sibling another.
- Interrupt patterns by affirming kids outside of their assigned family roles
- Create psychological safety so kids don’t have to compete for visibility
- Recognize when success is reactive, not self directed. The high-achiever may be carrying invisible pressure
- Make time for each child individually so you can appreciate the unique person they are and bond you have with them. Being seen and understood helps children feel confident in who they are and their place in the family. It decreases sibling fighting and strengthens household connections because no one is fighting for precious parent time.
Siblings are an impactful teacher for each other. From pretend play that helps them role play social dynamics for the real world, to being a best friend and confidant. It is an amazing gift to give – a person who knows you like no other for all your life if you’re lucky.
References:
Dominus, S. (2025, May 6). The surprising ways that siblings shape our lives. The New York Times Magazine. https://www.nytimes.com/2025/05/06/magazine/siblings-families-parents-influence.html
McHale, S. M., Updegraff, K. A., & Whiteman, S. D. (2015). Sibling relationships and influences in childhood and adolescence. Journal of Family Psychology, 29(5), 627–634.
Lareau, A. (2011). Unequal childhoods: Class, race, and family life. University of California Press.
Zang, E., & Goodman, J. (2022). Sibling spillover effects and educational achievement. Frontiers in Psychology, 13, 834721. https://doi.org/10.3389/fpsyg.2022.834721
