And Prince William and Kate Middleton's own account even got in on the action, posting a smiley photo of the birthday boy along with a message of thanks for all the well wishes.
"This long-planned move will ensure that permanent support arrangements for The Duke and Duchess's work are in place as they start their family and move to their official residence at Frogmore Cottage", a statement from the Royal family at the time said.
Harry and Meghan's insufficient greeting only adds to the rumors going around that the blue blooded brothers are not as close as they once used to be.
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When Harry and Meghan's engagement was revealed in 2017, Kensington Palace announced the former actress was giving up her own charitable interests to begin work with the Foundation.
It's uncommon for siblings in the royal family to have collaborative charities and foundations like this in the first place, according to Koenig, who thinks the only reason for the joint venture from the beginning was for both brothers to have a project to share as they grew up.
Prince William, second in line to the British throne, is celebrating his 37th birthday in private on Friday.
Harry and Meghan have already split from the Cambridges' Kensington Palace household, setting up their own at Buckingham Palace in the spring, with a separate head of communications and SussexRoyal Instagram account.
There also have been hints that Meghan might spend some time in the United States with or without Harry.