Prince William, the Duke of Cambridge and second in line to the British throne, is celebrating his 36th birthday today (June 21). He's married now with three young children of his own, but we'll always remember Princess Diana's older son from his days as a handsome little prince. Pictured here, Princess Diana helps her three-year-old son solve a puzzle. Visit the link in our bio to see a young Prince William through the years. _ Follow gettyarchive for more pictures of people, places and moments that are shaping history. _ 📷: Tim Graham/Getty Images | #Royals #HBD #PrinceWilliam #PrincessDiana #LittlePrince #tbt #ThrowbackThursday #Archive