There have been rumours of a rift between the Sussexes and the Cambridges for some time.
And on Prince William's 37th birthday, Meghan and Harry have sent a very formal birthday message on social media fuelling speculation of tension between the two brothers.
Kensington Palace's official Instagram feed paid tribute to its royal inhabitant.
"Thank you everyone for your lovely wishes on The Duke of Cambridge's birthday!" it said.
The Duke and Duchess of Sussex's account was quick to wish Prince William a happy birthday by leaving a message.
"Happy Birthday to The Duke of Cambridge!"
In recent months, Meghan and Harry have cut ties with Kensington Palace.
The couple - and their baby, Archie - has created its own royal household based at Buckingham Palace.
It was also revealed that they have left The Royal Foundation, a charity set up by Harry and brother William.
And Instagram followers were quick to point out the formal nature of the birthday message.
One follower replied: "@sussexroyal you can't even do your own post for your brother? That just seems tactless, especially when it is said that Meghan runs the page. Interesting way to feed the rumors."
Another wrote: "Why not just post a happy birthday on your page like the other royal pages?
"Although it's your page it is OK for you to post the other royals faces you know. Very strange the way your page works like you don't want the faces of any other royals on it."
A third person commented, "It's your own brother, why the need to be so formal?"
"Wouldn't wishing your brother be more gentle? This reads like there is hostility," wrote a fourth.
However, other followers also made the point that the Duke and Duchess of Sussex can't win whatever they do!
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