The intertwined lives of sister best friends

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Carley Hawkins (L) and Lauren Cummings
Sisters often weave their lives closely together. In some cases, it's the most significant bond they have – but it's not without complications.

Lauren Cummings and Carley Hawkins have a deep understanding of life with a sister as a best friend. Growing up in Portsmouth, England, the siblings attended the same schools and swam competitively, meaning they spent most of their free time together. During university, they lived at home and worked part-time in the same supermarket. 

Now Lauren, 35, and Carley, 38, have jobs in different departments of the same university, and meet several times a week for lunch or to exercise. They often hang out in the evenings and weekends with their children and families, too. Each plays a fundamental role in the other’s life, from being a round-the-clock confidant to serving as a tireless source of moral support and encouragement in personal and professional decisions. 

“We are each other’s biggest cheerleaders and as the eldest, I will always be fiercely protective of Lauren,” says Carley. “We know we are there for each other, no matter what.” 

For Lauren and Carley, theirs is a joyful, nurturing relationship that adds to their lives. This makes sense; research shows that positive sister-sister bonds can boost confidence, offer constant companionship and even increase feelings of self-love. Indeed, 2020 research published in the Journal of Family Psychology found that sister-sister pairs are most likely to report warm relationships compared to other sibling gender compositions. 

However, sisterly closeness can also come with tensions. Being too intertwined as siblings can make it harder to form an individual identity. Plus, intense bonds can impact other friendships and cause friction in – or even end – romantic relationships. This means that finding a balance between a healthy friendship and a healthy sisterhood isn’t always easy.

Lauren (L) and Carley rely on each other for emotional and practical support (Credit: Lauren Cummings (L) and Carley Hawkins)

Lauren (L) and Carley rely on each other for emotional and practical support (Credit: Lauren Cummings (L) and Carley Hawkins)

 ‘She gets me like nobody else’

 “You can choose your friends, but not your siblings – they are a constant shadow in your life, for better or for worse,” says Geoff Greif, a professor of the University of Maryland School of Social Work, US, and co-author of Adult Sibling Relationships. “According to our research, though, most people are close with their siblings, and best-friend relationships with them are not uncommon.”

Megan Gilligan, an associate professor in human development and family studies at Iowa State University, US, who co-authored the 2020 research, says close ties are more likely among sisters because women, in general, tend to have closer interpersonal ties. “Daughters are socialised to be more expressive with their emotions and feelings, and to value and place greater emphasis on relationships than men,” she explains. “Sons are encouraged to pursue instrumental achievements outside the family – women are likely to place greater value on their roles as sisters than are brothers.”

As Gilligan explains, women often play the ‘kin keeper’ role in family relationships, serving as confidants, planning family events and keeping family members updated on each other’s lives. As such, sisters are more likely to be open with each other. “They also typically spend more time together and provide each other with support, more so than any other gender combination,” says Gilligan. The contact and support is likely to foster emotional relationships which hold fast as sisters grow older – compared to men, women report less decline in sibling contact as they age.

Data suggests that having sisters brings benefits from an early age; US researchers found that having a sister protects young teens from feeling lonely, unloved, guilty, self-conscious and fearful. Another study showed that young people with sisters are more independent and goal-oriented than those with brothers. Just having a sister living nearby has been associated with greater life satisfaction.

“We are the first person the other goes to with a problem,” confirms Lauren. She’s recently been particularly appreciative of her sister’s emotional support as she moves through a split with her long-term partner. The mutual help is also practical; Lauren and Carley rely on each other to cover any childcare gaps and their children, both aged four, are inseparable.

She gets me like nobody else on the planet gets me - more than an intimate partner, parent or a friend - Christina

Identical twin sisters Jessica Dunagan and Christina Brown, who live in Washington, US, are in a similar position. “We have helped raise each other’s kids, and it’s like they have two moms – getting double guidance and double protection,” says Jessica. 

Jessica and Christina tend to know what the other is going through, even when apart. “As twin flames, we feel each other’s lives and have always experienced life in parallel,” explains Christina. “We met and married people at the same time, got pregnant at the same time - she gets me like nobody else on the planet gets me - more than an intimate partner, parent or a friend.” 

The sisters, who run an intuitive life-coaching business together, text each other first thing in the morning and agree that living two minutes apart by car is the ideal distance. “It sounds crazy, but if we lived further away from one another, we’d live our lives in complete panic and anxiety,” says Christina. They haven’t ever clashed over business matters, and have even written a book together.

Jessica (L) and Christina's closeness has interfered with romantic relationships in the past - but they are working on boundaries (Credit: Jessica Dunagan (L) and Christina Brown)

Jessica (L) and Christina's closeness has interfered with romantic relationships in the past - but they are working on boundaries (Credit: Jessica Dunagan (L) and Christina Brown)

When closeness causes conflict 

However, while close sisterly bonds can be immensely rewarding, they can also come with potential downsides. With sisters more likely to be in regular contact, there are more opportunities for conflict. “Overall, women tend to be engaged in their family relationships, so they’re more likely to experience both the positive and negative dimensions of these ties,” says Gilligan. 

Being very close to a sister can also lead an individual to prioritise a biological bond over other nourishing friendships. From young adulthood onwards, friendships positively influence self-worth, social acceptance and adaptability. Healthy young adults tend to have a network of social supports that comprises close connections with friends as well as family members. Dense family networks, or people who focus primarily on family, are found to have less contact with non-family, and this reduced variety in their network can make them more vulnerable if family bonds suffer or break. 

Both Carley and Lauren have a network of close friends, some of whom they have known for decades. “I have different relationships with each of my close friends, which is linked to what stage of life we met, and I would go them for different things,” says Carley. “But the connection is completely unique with Lauren, because we have our own language and understand what the other is thinking or feeling without words.” 

Lauren and Carley’s partners have largely appreciated their close bond – but intense sibling closeness can cause tensions between a sister and their romantic partner. “One of my exes didn’t understand our connection and the desire to spend so much time together,” says Lauren, “but he wasn’t close to his family at all, so it was completely new for him.”

Family Tree

This story is part of BBC's Family Tree series, which examines the issues and opportunities parents, children and families face today – and how they'll shape the world tomorrow. Find more on BBC Future.

Jessica and Christina have struggled more in this area; their close bond has caused clashes with all of their partners. “I can bluntly say my sister is my number one, and I’ve been told that’s not healthy. But guys come and go, but my sister is here for a lifetime, from conception to death,” says Christina. The twins have also disagreed over each other’s choice of partner. Jessica doesn’t understand Christina’s taste in men, for example, and has in the past wanted a say in who she picks. 

At one point, tensions reached breaking point. After their first marriages ended in divorce and Christina met someone new, she cut off Jessica for three months. “I needed to figure out who I was as an individual and I knew I was only going to do that by being isolated, with none of her influence,” explains Christina. 

The abrupt severance hit Jessica hard; she had daily panic attacks and describes it as the darkest period of her life. “It was the first time I experienced loneliness,” she says. “I’m 39 years old and used to always having her around – when it got ripped away from me, I didn’t know how to survive.” 

As Greif points out, “romantic relationships can be the flashpoint into tensions on any number of levels”. And when conflict arises between sister-best friends, it can be hard to cope with. Drifting away from a friend, while upsetting, can feel natural and mutual. Stepping away from an established routine with a sister-best friend, however, is likely to have deeper ripples that can be destabilising. “When there is estrangement, it can cause a sibling to question their ability to establish intimate relationships [as a whole],” says Greif. 

A need ‘that will never change’ 

Since the three-month separation, the twins have made a point of redrawing boundaries between them, staying out of each other’s relationships and reducing controlling behaviours. “In the past, we always tried to make decisions for one another and push opinions about how we should live our lives,” explains Christina. “We’re getting better at keeping those opinions to ourselves.”

Unlearning years of patterned behaviour may not be easy. “When we get upset at our partners, we run to each other to vent, which can get messy – we know it’s not healthy,” notes Jessica. But the benefits of working to preserve a healthily close relationship are clear. As Greif points out, sisters will know each other longer and better than anyone else in their lives – longer than parents, partners or friends. “They share history and when that history is good, it can continue to rejuvenate sisters as they remember good times and join together with newer partners and families, and care for aging parents,” he says.

Jessica and Christina are pragmatic about how being sister-best friends might play out after their break. “We know our relationship will always be a work in progress and something we need to work at every day,” says Jessica. “We want to find easier ways to be sisters and still have some independence, but also accept that there are some things we need from each other that will never change.”