Prince William and Kate were the first members of the royal family to publicly celebrate the birthday of Prince Charles. The touching picture shows the Prince of Wales holding the small hands of a mischievous prince, Louis, held by the Duchess of Cambridge.

The publication on Instagram reads: "I wish the Prince of Wales a happy birthday!"

The heartfelt message also includes two other images, one representing princes Charles and William William smiling and the other with Prince William and his brother Harry surrounding their father.

The photo of Charles, Kate and Louis was first published last year to celebrate the 70th birthday of Prince Charles.

On this occasion, the palace published a series of photos with the Cambridges, Harry and Meghan Markle and Camilla, the Duchess of Cornwall.

But that's Prince Louis, born in April 2018, who stole the show that day.

In a photo, we see the little royal snuggle into the arms of his grandfather.

In another case, the smallest member of the royal family at the time disrupted a group photo by placing his tiny hand on the face of the Prince of Wales, leaving everyone in the mesh.

And in another, we can see Louis smiling confidently at the camera in the arms of his mother Kate.