How Your Siblings Shape Your Personality

What experts say about their power of influence

Photo: Klaus Vedfelt/Getty Images

OOne of the few joys in the weeks of recent, unending awful news surrounding the novel coronavirus has been the emergence of Andrew and Chris Cuomo as sibling rivals. We’ve watched Governor Cuomo, the elder brother, and Chris, the CNN anchor, bicker on-air about calling their parents and which one is their mother’s favorite. We’ve heard about the younger Cuomo’s fever dream in which his brother donned a ballet costume. (Chris Cuomo was diagnosed with Covid-19 at the end of March.) It’s funny to think about these two people, who are major voices in the world right now, growing up under the same roof — the ways in which their early years together might have influenced the public figures they are now.

As a kid, I often felt like my younger sister and I were in the lyrics from a bad pop song. The kind that uses two very different types of women as foils for each other. She was class vice president and a cheerleader and I couldn’t dance or win an election if I bribed people to vote for me. (Which I might have considered, unlike my sister who would never.) Real life is, of course, more nuanced than a Top-40 tune. School came pretty easily for me, largely because I enjoyed it. For Bailey, my sister, it was more a means to an end. (We work for the same company now, so really it all evened out eventually.) Bailey was quiet, whereas I fed on talking to anybody and everybody. The short of it is we both spent a decent amount of time in our formative years trying to become more like each other. Now that we’ve grown up and can look back with the perspective and necessary humor that hindsight affords, it’s interesting to think that during all those years we spent fighting and growing and bonding we were actually shaping the adults we would grow to become.

I’m certainly glad for that experience, but I figured I should ask my sister, too. Give her a chance to have a say in the matter, something I didn’t always do when we were younger. “I think since we were living under the same roof, I was often influenced to do a lot of the same things as you,” Bailey said. “It wasn’t until we were older that I think you specifically influenced my personality. Or at least influenced my personality enough that I was aware of it.” She mentioned the time she joined our high school’s Quiz Bowl team (it’s like team Jeopardy and, where we’re from, it actually counts as a varsity sport). “I did it because you were the ‘smart’ one,” Bailey told me, laughing about how she wasn’t very good. I asked her the opposite question: If there were things she feels I influenced her not to do. “You were such a know-it-all,” she said, laughing. (Fair.) “And you let people know it.” (Also fair, hence the Quiz Bowl team.)

DDepending on who you ask in the field, having a sibling is either a huge influence on your personality, very little or even no influence, or some combination of the two. “One of the things that I had to do when I was writing this book was to hold two contradictory premises in my head at the same time,” Jeffrey Kluger, author of The Sibling Effect: What the Bonds Among Brothers and Sisters Reveal About Us, told me. “Siblings are some of the most primal and powerful shapers of who you will become. They serve as our dress rehearsal for life. They serve as our civilizers. They teach us how to conduct disputes, how to resolve disputes, and when to avoid disputes. They teach us about confidentiality, they teach us about support, they teach us about independence, all of these fundamental things that serve, essentially, as your dry run for life. And yet, at the same time, if you were an only child, you’ll do just fine.” (Only children reading this, you can exhale now.)

Christine B. L. Adams, psychiatrist and author of Living on Automatic: How Emotional Conditioning Shapes Our Lives and Relationships, told me our personalities are predominantly shaped by our parents, or the people who raise us, and that our personalities are often finished being formed before we reach an age where we’re at all cognizant that it’s happening, around the age of three. “Siblings don’t create personality because they’re too young,” she said. “The only people that really have an effect are whoever’s taking care of you, whatever adults are taking care of you.” Kluger echoed her arguments that parents are definite shapers of our personalities, but preferred a less-binary approach. “Parents can make you a cold or remote person or shape you into a warm and very accessible person, within certain limits, he said. “But they do that top-down. Siblings do it in a group, in real life, by living those lives together, as opposed to taking the lessons and obeying the instructions that come from above.”

Siblings are some of the most primal and powerful shapers of who you will become. They serve as our dress rehearsal for life.

Kluger told me one of the biggest reasons he believes siblings form us as people is that our siblings are “the only relationship in your life that’s with you for the entire ride.” (There’s obviously some flexibility here depending on the age gap between you and your siblings.) “They’re with you from the moment you enter the world. They stay with you as you age, they stay as you mature, they stay with you as you go out into the world, presumably, if it’s a healthy relationship,” he said.

BBailey and I molded each other in ways that aren’t quite as quantifiable as her single semester as a Quiz Bowl interloper. I told her I thought the easiest example for me to identify was how being her sister made me a better listener. Or, at least, made me aware that I needed to work on being a better listener. “You were so shy, but you always had things you wanted to contribute to the conversation if I’d shut up long enough to let you,” I explained. “True,” she said, agreeing with me when I said I don’t think she’s shy anymore. Then we exchanged a very dry “you’re welcome” and “thank you” as only people who have been picking on each other for decades can do.

“I had an easier time making friends, but you were the extrovert who could walk up to anyone, at any age, and have a conversation with them,” Bailey said. “I still struggle with that but I think being in all those situations with you I was forced to put myself out there.” Kluger explained this as the way we use our siblings “as both positive role models and as cautionary tales.” “If your sister was navigating the world badly, say academically or socially or behaviorally, you might think, ‘well, you know, she’s in a world of hurt all the time, and I simply don’t want to be that way.’”

Even though we share a distinctive last name, our coworkers don’t always realize that we’re siblings. “People aren’t saying, ‘Ah, yes, your personalities are so similar! How did I not put that together before,’” Bailey said. But working together has meant we’ve gotten to continue, perhaps more forcefully than other siblings, to exert our respective gravitational pull on each other. “I really still think of you as ‘the chill one’ and having you around is a good reminder that I could always better emulate that,” I told her. “That’s because I am the chill one,” she, correctly, teased. “But I’m also still the one who has to really try to put myself out there to people when I’m in meetings. I feel I make myself do that more because, being related to you, I have something to prove. That can be a good driving force.”

Finally, we talked about, well, the way we talk. “I definitely mimicked your wit [as a kid],” Bailey said. I told her I frequently feel like she’s the best audience for my jokes — and vice versa — because I know chances are good she’ll get even my most obscure reference. “I think you’re one of the funniest people I know and I think that’s probably because we honed our senses of humor together,” I explained. “You know you basically just said you’re the funniest person you know, right?” she, ever the little sister, said. I wonder if the Cuomos think each other are funny, too.

Madison Malone Kircher is a staff writer at New York Magazine. She lives in Brooklyn. Twitter: @4evrmalone

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