Kate Middleton, who is celebrating her 43rd birthday on Jan. 9, has proven herself to be the shiniest jewel of the British monarchy. The princess is married to Prince William, heir to the throne.

The Princess of Wales said her cancer diagnosis came as a "huge shock." Kate Middleton and Prince William share three kids: George, Charlotte and Louis.

Prince William said Princess Kate was "the most incredible wife and mother" and including a message from their children.

ANALYSIS: Royal Editor Emily Ferguson discusses the hidden messages in Prince William's emotional tribute to his wife.

Prince William celebrated wife Kate Middleton’s 43rd birthday with a touching tribute heralding her ‘strength’ over ‘the last year’ as she battled cancer

Prince William took to social media to share an extremely personal message to his wife Kate as she celebrates her 43rd birthday today along with a brand new beautiful picture of her

Prince William lovingly paid tribute to the Princess of Wales's 'remarkable' strength as he shared a touching birthday post

It’s an unusually personal message from the Prince, but one that chimes with the Waleses’ newfound candour following the Princess’s cancer diagnosis and recovery over the course of 2024.

The Princess of Wales is celebrating at home in Windsor with the Prince of Wales, with Prince George, Princess Charlotte and Prince Louis spending the day at school before a family celebration in the evening.

The Prince of Wales has wished his wife, Catherine, a happy birthday as she turns 43. "To the most incredible wife and mother. The strength you've shown over the last year has been remarkable," William wrote in a message posted on social media.