The Royal Family is marking Prince William's 39th birthday with well-wishes on Monday.

Prince Charles, William’s father, posted an old black-and-white photo of himself holding his eldest son as a baby, as well as a second photo posted by Charles features himself alongside his wife, Camila, and William at an event.

In his tweet, Prince Charles wished his son “A very Happy Birthday” with a short message that included a birthday cake emoji.

The Royal Family's official Twitter account also shared four photos of William at various functions, including one featuring his wife, Kate, and his three children, George, Charlotte and Louis.

A day prior, William and Kate celebrated Father's Day by sharing old family photos, including one that was previously unseen by the public.

William shared a message on social media Monday, thanking the public for "all the birthday wishes and kind messages."

For the Duchess of Cambridge, June 21 is doubly special as it also marks the wedding anniversary of her parents, Carole and Michael Middleton.​