Prince William and Princess Kate are celebrating their wedding anniversary with a throwback photo.

The Prince and Princess of Wales on Monday marked the 13th anniversary of their wedding by sharing a never-before-seen black-and-white photo from the day of the ceremony. "13 years ago today!" they wrote on their official Instagram and X accounts, crediting the picture to Millie Pilkington.

William and Kate's royal wedding was held on April 29, 2011, at London's Westminster Abbey. Between 2013 and 2018, they welcomed three kids: Prince George, 10; Princess Charlotte, 8; and Prince Louis, 6.

Last year, the couple celebrated their 12th wedding anniversary by sharing another previously unseen picture, albeit more casual than this year's: It showed William and Kate both wearing jeans and sunglasses while standing over bikes.

William and Kate's 13th anniversary comes amid a tumultuous year for the couple. In March, the Princess of Wales shared that she has been diagnosed with cancer after undergoing planned abdominal surgery in January.

"This of course came as a huge shock, and William and I have been doing everything we can to process and manage this privately for the sake of our young family," Kate said in a video message. "As you can imagine, this has taken time. It has taken me time to recover from major surgery in order to start my treatment. But most importantly, it has taken us time to explain everything to George, Charlotte and Louis in a way that is appropriate for them and to reassure them that I'm going to be OK."

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William and Kate were both subsequently absent from Easter service on March 31. But the Prince of Wales made his return to his official duties earlier this month, paying a visit to a charity that redistributes surplus food.

The Prince and Princess of Wales were both "enormously touched by the kind messages" they received following Kate's cancer diagnosis, a statement released in March by Kensington Palace said.

Happy birthday, Prince Louis!Prince William, Princess Kate celebrate with adorable photo

"They are extremely moved by the public's warmth and support and are grateful for the understanding of their request for privacy at this time," the statement said.

The anniversary post comes after William and Kate recently shared a photo of their son Prince Louis to celebrate his 6th birthday.

"Happy 6th Birthday, Prince Louis! 🎂," they captioned the photo. "Thank you for all the kind wishes today."

Contributing: Naledi Ushe, USA TODAY