Is your relationship with your sister subtly shaping all your friendships?

From always putting others first to never quite feeling included, the role you play in your friendships may have been shaped decades before you even met your closest friends.

We tend to think of friendships as something we choose freely as adults. We meet people, we connect, and we decide who feels right for us. Yet many people notice the same emotional patterns appearing again and again in different friendships, even when the people involved have nothing in common.

Some always end up taking care of others. Some feel they are never fully included. Some seem to occupy the centre of attention wherever they go. The names and faces change, but the position feels strangely consistent. Therapist Marisa Peer believes those positions are often shaped long before adulthood.

“If you have a brilliant sister or a pretty sister and you’re often in her shadow, then that’s the only pattern you know, and you repeat that pattern. I love this expression: ‘we play the only part we’ve ever known, then we make that part our very own.'”

Familiar dynamics, different faces

In her view, sibling relationships are not simply early experiences. They become emotional templates for later relationships, particularly friendships. What matters is not only the role a child occupies, but what that role teaches them to expect.

If someone grows up feeling undermined within a sibling dynamic, Peer suggests that experience can become familiar rather than alarming. It does not necessarily register as something to avoid in adulthood. Instead, it can feel like the shape close relationships are supposed to take.

“If your first memory is you’re not liked,” she says, “then in a friendship you’ll often tolerate being not liked, or tolerate being picked last, or tolerate people being a bit mean to you.”

Why belonging still feels so important

For Peer, sister relationships carry particular emotional weight because they are closely tied to our sense of belonging.

“We had to be bonded to the sisterhood,” she says. “If the other women liked you, they would give you food or look after your kids. And if they didn’t, you just couldn’t survive.”

That ancient need for connection, she argues, still echoes today.

“If you have a sister who doesn’t like you or undermines you,” she says, “you start to feel very, very unsafe, because we’ve always needed the sisterhood to make it.”

These dynamics are reinforced through behaviour as much as expectation. If being overlooked is familiar, it can become something that is quietly accepted. If being central is familiar, it can become something that feels necessary to maintain.

That sense of belonging as safety does not disappear in adulthood. It simply changes form. Group approval still carries emotional weight, even when survival is no longer at stake.

It is part of why friendship groups can feel so emotionally charged, even when nothing explicit is happening. Inclusion still feels stabilising. Exclusion still feels deeply personal.

How birth order can shape your friendships

The pattern can operate in the opposite direction as well. Someone who learned early that they were the dominant or highly visible figure within the family may carry that expectation into friendships, naturally becoming the organiser, the leader or the person others look to. Not because it is consciously chosen, but because it is the role that has always felt familiar.

Birth order can reinforce those patterns too. Peer suggests that older sisters often continue acting as carers within friendship groups, becoming the friend who steps in during a crisis, checks in when someone is struggling or quietly takes responsibility for everyone else. Younger siblings, meanwhile, may continue playing the role of the attention-seeker or rebel long after childhood has ended.

Again, the point is not that these roles are fixed, but that they often feel automatic.

When a pattern starts to feel like personality

What makes these roles so powerful is how normal they can feel to the person living them. They do not present themselves as patterns. They present themselves as personality.

The caretaker is simply dependable. The quieter friend simply doesn’t like attention. The dominant friend is simply outgoing. Yet each of these positions may have been rehearsed long before adulthood.

Peer also believes that changing these patterns sometimes starts by changing the way we think about the relationship itself.

“You have to kind of redefine them,” she says. “Start not to see your sister as your sister, but to see her as a friend, or a confidante, or a colleague… Once you change the label you’ve given someone, it gets easier to understand — and not tolerate — certain behaviours.”

It is a subtle shift, but an important one. Childhood roles often survive because we continue relating to people through the identities they held decades ago rather than the people they are now.

Words: Lucy Rawlinson, Images: Shutterstock