London, UK - Kate Middleton honored her husband, Prince William, on his birthday with a rare photo of him with the royal couple's three children.

The Prince of Wales turned 42 on Friday, and in celebration of his big day, Kate shared a sweet message alongside a photo of William with their little ones.

"Happy birthday Papa, we all love you so much! Cx," the Instagram post read.

The Princess of Wales was credited as the photographer behind the snap, which shows the quartet holding hands as they jumped together on a beach.

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The post comes after Kate made her long-awaited return to the public eye for her first royal outing after her abdominal surgery in January.

The royal disclosed her cancer diagnosis two months later, and she has been out of the limelight ever since.

Though her attendance at the annual Trooping the Colour was certainly a positive sign for her ongoing treatment, Kate herself confirmed she's "not out of the woods yet."

"On those bad days you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well," she said in a recent update.