Prince William marks Kate Middleton's 43rd birthday with a rare gesture by expressing his love.

The Princess of Wales was casual in jeans for her birthday portrait.

Prince William marks Kate Middleton's 43rd birthday with a rare gesture by expressing his love.
Prince William marks Kate Middleton's 43rd birthday with a rare gesture by expressing his love.

Prince William is celebrating his wife Kate Middleton on her 43rd birthday.

On Thursday, the Prince of Wales posted a previously unseen black-and-white portrait of the mother of three on the couple's social media.

"Catherine, on her birthday, William, 42, wrote a heartfelt caption to his wife and mother, expressing his admiration for her strength and resilience over the past year. The family, including George, Charlotte, and Louis, are incredibly proud of her."

"We love you. W," he closed the message.

The Prince and Princess of Wales usually avoid writing personal messages on social media, but a recent post by William was a rare public declaration of his love and support for his wife, who completed chemotherapy treatment in September.

Last summer, in Windsor Castle, Matt Porteous captured a photo of Kate wearing a plaid scarf, white T-shirt, jeans, and a blazer.

The Princess of Wales, with a beaming smile, finished off her casual attire with her mother-in-law's sapphire and diamond engagement ring, which she wore proudly.

Prince William looking at his wife Kate Middleton who is smiling.
The Prince and Princess of Wales married in 2011. They share three children. (Chris Jackson/Getty Images)

According to British royal expert Hilary Fordwich, Kate is currently at home at Adelaide Cottage, Windsor, with William and their children, Prince George, Princess Charlotte, and Prince Louis.

"Although they typically remain at Anmer Hall in Norfolk for Princess Catherine's birthday, this year they returned early to Adelaide Cottage to ensure their children could attend school. As a devoted and engaged parent, Catherine prioritizes her children's education above her own birthday celebration."

"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." — Prince William

Fordwich stated that since it is her birthday and it is a school day, despite Prince William's admission of not being an exceptional cook, he is renowned for preparing a fantastic breakfast, which he might have made for her this morning.

Kate Middleton looks happy as she appears in a video to update the public on her cancer battle
In September, Kate Middleton announced she was "cancer free" after completing chemotherapy treatments. (Will Warr)

In December 2024, Kate announced that she was undergoing treatment for cancer. During her Christmas carol service, the princess admitted, "I didn’t know this year was going to be the year that I’ve just had."

According to Robert Hardman, author of "The Making of a King: Charles III and the Modern Monarchy," Kate is gradually resuming her royal duties while prioritizing her well-being.

WATCH: KATE MIDDLETON ANNOUNCES SHE HAS COMPLETED CHEMOTHERAPY TREATMENT

Kate Middleton announces she has completed chemotherapy treatment

"Cancer doesn't follow a predictable pattern, and we should not view it as a chapter that's over, followed by a return to normalcy," said Hardman. "The specifics are private, but the reality is that cancer is an unpredictable disease."

Hardman revealed that the key to her approach to completing chemotherapy is in the phrase "one day at a time," as she announced in September.

by Stephanie Nolasco

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