Sisters tend to be close – so why do sisters-in-law so often go to war with one another?

Sister-in-law dynamics are complicated and competitive. Just look at the famous rift between Kate Middleton and Meghan Markle. Anya Meyerowitz speaks to the experts about why these relationships can be so difficult to manage, and how to make them better

Feuding sisters-in-law Meghan Markle at Kate Middleton at Wimbledon in 2018 (Getty)

My favourite time of day is whatever time my sister happens to call. The content of the call is immaterial – sometimes it’s an anecdote from her day or an off-loading of mine, other times it’s a joke or a memory that’s happened to pop up – it really doesn’t matter, as long as she’s on the other end of the line.

And there will be other women across the country, the world even, who feel the same way about their sister. If you’re one of them, you’ll be less than surprised to know that, according to a recent study, relationships between sisters can be more rewarding and more positive than any other bond between siblings. Most prior research on siblings has found that conflict decreases and intimacy increases as siblings get older and move out of the nuclear family home, but until now there hasn’t been a lot of digging done on whether these patterns differ by sibling gender and position in the family.

To reach their conclusion, researchers from Pennsylvania State University dived deep into a study of 201 families that began in 1995 and continued across 18 years, with 61 families remaining at the end. Findings indicated that, while levels of intimacy and conflict might ebb and flow across life events, the bond between sisters had the most positive impact of any sibling, or family member pairing. And though intimacy would decline until adolescence, it would substantially increase thereafter, levelling off in early adulthood, while the opposite was the case for conflict.

However, not all “sisterly” bonds are so amiable; when it comes to sisters-in-law, the story is a very different one – in fact, experts often dub it one of the trickiest relationships a woman might face among family dynamics. Indeed, if you type “sister-in-law relationship” into Google, prompts like, “How do you deal with a difficult sister-in-law?” and “Why doesn’t my sister-in-law like me?” pop up immediately, and Reddit is littered with people asking for advice on how to navigate a less than straightforward relationship with their sister-in-law.

It’s a struggle I know all too well, because – although we are on good terms now – my own relationship with one of my sisters-in-law felt upsetting, complicated and anxiety-inducing for many years. I can’t count on one hand the number of times I drove away from my in-laws in floods of tears, sobbed down the phone to a friend from the safety of my bedroom or experienced an intense unease in the run-up to a family event.

And less than desirable relationships between sisters-in-law are everywhere, and they play out in the media all the time. Most famously, there’s the royal rift between Kate Middleton and Meghan Markle which, according to Prince Harry’s memoir Spare, started soon after he and his now-wife became engaged and escalated from there. His book documents many examples of feuding between the sisters-in-law, including one infamous incident that Meghan herself referenced in her interview with Oprah, where Kate was allegedly difficult about Princess Charlotte’s bridesmaid dress, causing an already-stressed Meghan to break down in tears. “She owned it, and she apologised, and she brought me flowers and a note apologising and she did what I would do if I knew that I hurt someone,” Meghan told the TV host during a tell-all interview in 2021.

A second, widely-reported incident involving the sisters-in-law came about when Meghan referred to Kate as having “baby brain”. Harry later confessed in Spare that his brother Prince William and sister-in-law Kate didn’t respond to the comment favourably. Kate apparently confronted Meghan, saying, “You talked about my hormones. We are not close enough for you to talk about my hormones.”

Then there are the myriad examples peppered throughout popular culture, from the fraught relationship between Alexis Colby and Krystle Carrington in TV hit Dynasty to Scarlett O’Hara and Melanie Hamilton’s sister-in-law “bond” in Gone With the Wind.

The question is, why is this dynamic so difficult? On average, women have more close friends and larger networks of social connections than men do, and tend to be better at garnering friendships, so what is it about the sister-in-law relationship that can trip so many of us up?

“The sister-in-law dynamic can be challenging for a variety of psychological and social reasons, instilling feelings of jealousy and competitiveness,” says relationship therapist and mental health expert, Sophie Cress. “Sisters-in-law may come from various families, each with their own set of values, customs, and expectations. These differences can lead to misunderstandings and stress.”

The sister-in-law dynamics within the royal family are famously strained (Getty)

In fact, the sister-in-law relationship may present greater challenges than those with other in-laws, due to their unique combination of competitiveness, emotional intimacy, and cultural expectations, Cress highlights. “Unlike relationships with parents-in-law, sister-in-law relationships can be more ambiguous and fluid, making them difficult to negotiate,” she says. “Sisters-in-law may also find themselves in direct rivalry for duties within the family, such as hosting holidays or becoming the major confidante of a shared sister, which can aggravate tensions.”

She adds: “Gender relations also play a role. Women are frequently raised to value relationships and family harmony, which might increase sensitivity and emotional responses in these encounters.”

For Rebecca*, it was a combination of these reasons and more that were to blame for her “toxic” relationship with her now ex-husband’s sister. “My husband’s family were really close, which initially I was really excited about as mine weren’t,” she recalls. “But while his mum, dad, grandparents etc. were all really welcoming, his sister was always a bit frosty no matter how hard I tried. And when we got engaged, it got worse.”

While Rebecca was planning her wedding, she’d receive frequent passive-aggressive, “or just outright aggressive”, comments from her sister-in-law. “She once asked to see the guest list for the event,” Rebecca says. “When I showed her, she counted the number of guests on each ‘side’ and then proceeded to tell me that her parents would be offended about how many more people were coming from my family than theirs.”

Rebecca’s marriage lasted five years and, during this time, the relationship with her sister-in-law never eased up. “When we announced we were getting a divorce, I spoke with all of Ed’s* family, but I never heard from her,” she says. “I did send her a text but she didn’t reply.”

For Helen*, the rift with her sister-in-law is more down to a jostling for position. “We both married into the family around a similar time and I think we both were keen to really cement our place,” Helen explains. “It’s a loud family, and a big one, and making your mark and feeling comfortable in your role within it is tricky, so when you have this mirror being held up to you to show you perhaps what you should be doing differently, or maybe how people might be responding differently to someone else in a different position, it was just all too easy to feel tension towards each other, rather than support each other.”

A simple talk can often uncover misunderstandings and clarify the air

Relationship therapist and mental health expert, Sophie Cress

And though she reflects on why the dynamic unravelled as it did, she’s at peace with the way things stand. “We’re just really different,” she says. “I wouldn’t be drawn to her if we weren’t forced to spend time together through our husbands, and so I’m OK with not getting on. It feels too far gone now to really dig into and I think it could possibly cause more harm than good. As long as we can be civil when the whole family gets together so that no one else is impacted, that’s my main concern.”

The good news is that the sister-in-law relationship isn’t necessarily a lost cause – something I can attest to. Cress advocates for addressing the matter with “empathy and open communication”. “Begin by trying to comprehend her point of view and the reasons for her actions,” she says. “A simple talk can often uncover misunderstandings and clarify the air. Express yourself honestly and respectfully, using ‘I’ phrases to avoid seeming accusatory. For example, ‘I feel left out when decisions are made without me,’ can be more helpful than, ‘You always exclude me.’”

Another key strategy is to set healthy boundaries. “Determine what behaviours are acceptable to you and what you are willing to tolerate, and communicate these boundaries clearly,” Cress advises. “At the same time, make an effort to build a positive relationship by finding common interests and spending quality time together. Showing appreciation and acknowledging her positive qualities can also help shift the dynamic to a more positive one. Remember, patience and consistency are key; changing relationship dynamics takes time.”

But the question is, if it’s not possible to make a relationship harmonious, how can you manage it in a way that doesn’t impact your wider relationship with your partner or in-laws?

“The only way to manage this situation is to focus on what you can control: how you react. You can’t control your sister-in-law’s thoughts or behaviours,” says Emma Loker, therapeutic counsellor and founder of MindWrite, a copywriting service for mental health professionals.

“When you feel yourself getting worked up, take a deep breath; this tells your stress system to stop, and your relaxation system to kick in. Doing this will make it infinitely easier to respond in a cool, calm way.”

Thankfully, where my relationship with my own sister-in-law is concerned, several years in, an unplanned conversation led us to take responsibility for our own roles in the rift and we have been able to find common ground and move forward. In fact, it now feels like a friendship in its own right, and one that I find genuine joy in. It was a real journey, as so many of our relationships are, but ultimately we were brought together on the same road. So why not ride it together?

* Names changed