Happy birthday, Kate Middleton! Inside the Princess of Wales' plans with Prince William, Prince George, Princess Charlotte and Prince Louis.

After a challenging year, Prince William has shared a moving tribute to his wife, Kate Middleton, on her 43rd birthday describing her as “the most incredible wife and mother,” alongside a new portrait.

The Prince of Wales wrote that he and the couple’s three kids — Prince George, Princess Charlotte and Prince Louis — “are so proud” of Middleton.

William praised Kate for her "remarkable" strength in the post released on Thursday, Jan. 9 Prince William is celebrating his love and admiration for Kate Middleton as she marks her 43rd birthday. In a message posted to the couple's social media,

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.

Prince William. “To the most incredible wife and mother. The strength you’ve shown over the last year has been remarkable. George, Charlotte, Louis and I are so proud of you. Happy Birthday, Catherine.

Prince William made rare personal comments about his wife Kate Middleton in honor of her 43rd birthday. See the sweet tribute to the Princess of Wales.

Kate, the Princess of Wales, turns 43 on Thursday, capping what was a tumultuous year for the mother of three and wife of Prince William. Kate, who was born Jan. 9, 1982, is expected to spend her birthday privately with William and their kids -- Princes George and Louis and Princess Charlotte -- at home in Windsor, England.

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 is honoring his wife, Princess Catherine, on her 43rd birthday, calling her "the most incredible wife and mother."