Opinion: Sisters-in-law are not always friends. Just ask Kate and Meghan

Lydia Denworth’s most recent book is Friendship: The Evolution, Biology, and Extraordinary Power of Life’s Fundamental Bond.

Last July, when the Duchess of Cambridge and the Duchess of Sussex sat side-by-side in the Royal Box at Wimbledon, they looked an awful lot like two girlfriends hanging out. The world wanted that to be true. Among the many imagined ways Meghan Markle might have benefited the Royal Family was the hope that, in each other, Kate and Meghan would find a friend. They could be the very model of modern royal sisters-in-law, together.

But Meghan left for British Columbia and the tie between Meghan and Kate will probably be cut as surely as whatever grand opening ribbon the still-working royals will be snipping next week. The world has run headlong into the glaring difference between hope and reality when it comes to friendship and sisters-in-law. (Would we have anticipated the same of royal brothers-in-law? Probably not.)

Oh, it would have been fun if they had picked up where the Princess of Wales and the Duchess of York left off. One of the things we loved most about Diana and Fergie was their friendship. Remember when they poked a friend in the backside with their umbrellas at Royal Ascot? Some thought it unseemly, but the rest of us saw a shared sense of humour and friends having some silly fun.

But Diana and Sarah Ferguson were friends before they were sisters-in-law. Diana even had a hand in setting up Prince Andrew and Fergie. And, in the end, it wasn’t all so rosy. In the year before Diana died, she stopped speaking to Sarah, miffed over Fergie’s 1996 autobiography, My Story. Among other things, Sarah said she had borrowed Diana’s shoes – and her plantar warts.

Real friendship is not a fairy tale. It’s a warts-and-all relationship that has to be earned. The word friend is not categorical like cousin or sister-in-law. Except perhaps on Facebook, friend carries emotional weight. It signifies something about the quality and character of a relationship that is based on history and the content of repeated interactions. If we call a spouse or relative a friend, we do so to signal the texture and tenor of our relationship with that person that cannot be automatically assumed. There is value added.

To achieve such value, friendship requires several things. One is proximity. We make friends most often with the people we see most often. We presume Meghan and Kate have put in some hours. Beyond that Wimbledon sighting, we periodically saw them smiling and waving from the balcony at Buckingham Palace. But their interactions could have been limited to those photo ops.

On a related note, friendship requires time and lots of it. It takes about 50 hours to go from being an acquaintance to a friend and close to 200 hours to be a “best friend.” If Meghan and Kate have spent 200 hours together, that would be the equivalent of 40 to 50 lingering girls’ nights out. That seems unlikely.

Friendship also requires a little similarity. Most of us befriend people who are like us. Kate and Meghan are thin and beautiful, but are from different countries and different backgrounds. Meghan was married once already. Kate was Prince William’s college girlfriend. Before she married, Meghan had a successful acting career and financial independence. Before she married, Kate worked as a fashion buyer and for her family’s party planning business. But she was mostly known as William’s girlfriend.

The one thing they had going for them was what psychologists called “shared plight,” which can strengthen bonds intensely. In Meghan and Kate’s case, there is no one else in the world who knows so well what it is like to be them. Now that Meghan is a mother, too, that connection extends to being young mothers raising young royals. According to Sarah Ferguson, she and Diana burned up the phone lines discussing their predicament when they realized they were stuck in unhappy marriages inside the Royal Family. It cannot be a coincidence that the two divorced within months of each other.

With that in mind, let us hope that whether or not Meghan and Kate are or were friends, these two young royal marriages survive. The unions stand a better chance of that if everyone involved has a friend to rely on when times get tough. This is reason to hope Prince Harry and William’s relationship recovers. It’s also a reason not to worry too much about Meghan. When she flew back to Vancouver, her actual best friend, stylist Jessica Mulroney, was reportedly waiting for her.

Keep your Opinions sharp and informed. Get the Opinion newsletter. Sign up today.