Meghan and Kate. Photos / AP
Over the past few days, social media gossip has been led entirely by royal watchers speculating not over what bride-to-be Meghan Markle will wear on her big day, or whether the baby countdown will soon begin, but over a far bigger issue: that of her new sister-in-law by marriage.
One camp is convinced she and Kate Middleton will become the best of friends, sharing fashion tips and girls' nights in, while the other half are whipping up rivalry before the engagement outfit has even been returned to the wardrobe. (Meghan's was much more chic than Kate's blue Issa wraparound, is the general consensus.)
But it's not surprising we're fascinated. As sisters-in-law, wives to perhaps the most famous — and famously close — brothers in the world, it's inevitable the two women will be seeing a lot of one another. And unlike a friendship, a familial relationship with an equally high-profile woman of almost the same age (Meghan is 36, to Kate's 35) is a fait accompli. They'll have to get along — or at least they'll have make it look as though they do.
To date, there has been nothing beyond careful praise on both sides. As Harry explained, "William was longing to meet [Meghan] and so was Catherine."
"She has been wonderful," Meghan insisted.
Meanwhile, the Duchess of Cambridge was accosted on her way to an engagement and asked for her views on Meghan. "William and I are absolutely thrilled. It's such exciting news," she offered, rather formally, before adding: "It's a really happy time for any couple and we wish them all the best."
Of course, despite her words sounding somewhat starched, there's every chance she means it. Kate has been intrinsic to the Windsors for several years, and William will one day be King. Her life as a young and prominent royal, who grew up a commoner, must at times have been lonely, but Meghan looks likely to bring a sprinkle of Hollywood fairy dust to the monarchy. They may be laying foundations for a lifelong friendship, forged from their shared situation. But it's equally possible that the adjustment may be rather difficult at first — or even falter later; Diana and Fergie's relationship famously turned from friendship to rivalry, as both competed for royal and public favour.
Kate has risen to the challenge of her position with a learned formality, never putting a foot wrong, dressed appropriately whether for state visits or gym workouts, and is now pregnant with the fifth in line to the throne. She waited seven years from first date to proposal, and has settled into royal life as a mother. With her Kate Spade dresses and bouncy hairdo, she looks aeons away from dazzlingly relaxed actress Meghan, who joked with Harry in front of the cameras as if they were on a casual date at Pizza Express.
The populace has already taken to the new broom — a YouGov poll found 49 per cent have a positive view of Meghan, and there's no sense she and Harry are anything but equals, due to her career.
It's easy to imagine that, with less royal pressure on her (after Kate gives birth, Harry will become sixth in line and unlikely ever to rule), Meghan will be free to wear more daringly fashionable outfits, have more fun, and enjoy marriage to the more relaxed younger brother, while William and Kate deal with the traditional stuff.
Now Kate's sister Pippa is married and busy, the Duchess may find Meghan — on hand at Kensington Palace — a well-located confidante.
But when it comes to managing expectations, says psychotherapist and relationship expert Hilda Burke, there is no "normal" in sister-in-law-style relationships.
"I've seen plenty of cases where the sisters-in-law act as catalysts to improve a relationship between siblings," she says.
"In most of the couples I work with, it's still the woman who oversees their social life. The sisters-in-law become the instigator for increased communication between the siblings."
Although in Harry and William's case, this is unlikely to be an issue. "Of course, this can work the other way, with one wife failing to prioritise the other when it comes to choosing who they spend time with," adds Burke.
And that's where rivalry can creep in — more so when there are children.
We're yet to find out whether Prince Harry and Meghan will have any royal babies, but for many in-laws, a growing family is merely a means of competition — what happens when their children achieve things yours don't, or vice versa?
Catty comments over the Christmas dinner table are unwelcome at the best of times, let alone when their little one got the sought-after school place you hoped yours would.
The "enforced friendship" aspect of sister-in-lawdom can be difficult, agrees teacher Riya, 37*.
"When my husband's brother married Karen, I thought she was a bit needy but they seemed happy. But as time's gone on, I've realised she's very manipulative. I really dislike her, but I don't have a family, so my husband's has become mine.
"We see them often, and everyone assumes Karen and I are the best of friends. I have to be polite, but I'm constantly making excuses to avoid them. I can't say anything or there'd be a huge family rift," she says.
"I feel I'm stuck with her for life."
Even if you like a new sister-in-law, it doesn't mean you have anything in common, says Lucy, 42, a full-time mother.
Her husband's younger brother "has just got married to a dazzling woman, 10 years younger than me. She's French, a writer and, though she's friendly, I can't help feeling like an old frump by comparison."
Whereas she got married in the village church, her siblings-in-law "hired a boat and had a huge, lively party. I felt stupidly tearful all day — it was the contrast between our staid lives, and how much fun they seemed to be having.
"Her life is so different from mine, we'd never be friends naturally."
Her circumstances may seem, on the surface at least, similar to the Kate/Meghan conundrum.
But those differences can work beautifully, says Alice Wilcox, 45, a manager. "When I married Steve, I was in awe of his brother's wife. She was so elegant and successful," she says.
"But she couldn't have been more welcoming. We share jokes about Steve's weird family, and I'm an aunt to her lovely children.
"She has become one of my best friends. I think the key is not to go on first impressions — she later confessed she thought I was 'too cool' for her!
"The main thing is to create a new relationship between you," Wilcox says.
"It doesn't have to be defined by the family you've both married into — it can be a great source of support in its own right."
* Some names have been changed
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