The royal family Instagram account is getting ahead of the festivities and just shared Duchess Sophie's portrait before her birthday on Monday. However, there's one tiny detail that I almost missed—and it has nothing to do with her photos.

Kate Middleton will be joining Prince William, King Charles, Queen Camilla, and other royals at a black-tie dinner-dance celebration for Sophie, Duchess of Edinburgh's 60th birthday, a source tells 'The Sun.

Along with The King and Queen Camilla, Prince William and Princess Kate, who share a close bond with the Edinburghs, are said to be joining the festivities. The Princess of Wales and Duchess of Edinburgh are said to have a particularly strong relationship, with Kate viewing Sophie as a sort of "royal sister."

Sophie, the Duchess of Edinburgh is marking a milestone birthday! She turned 60 on Monday, Jan. 20, and friends and former colleagues have been honoring her contribution to the royal family – amid the release of the duchess' stunning new portrait.

The royal family has wished the Duchess of Edinburgh a very happy 60th birthday. Sophie’s milestone was celebrated on the British monarchy’s official social media accounts with a video montage of photographs of the duchess on royal engagements,

The statement continued, "As The Duchess looks ahead to turning 60, Her Royal Highness has a renewed sense of excitement and commitment to her work around gender equality and look

Sophie, the Duchess of Edinburgh is turning 60 in style. The royal—who marked her milestone birthday on Monday, January 20—released a trio of stunning portraits to commemorate the special occasion over the weekend that seemingly included a subtle sartorial nod to her grand new title.