Prince William has a new reason to celebrate.The Duke of Cambridge turned 39 on Monday – just a day after commemorating Father’s Day with his wife Kate Middleton and their three children: Prince George, 7, Princess Charlotte, 6, and Prince Louis, 3.William’s father, Prince Charles, took to Instagram early in the morning to share two candid photos in honor of his eldest son’s birthday.”Wishing The Duke of Cambridge a very Happy Birthday today!” the 72-year-old captioned the snaps on the official Clarence House page.PRINCE WILLIAM, KATE MIDDLETON RETURN TO COLLEGE IN ‘ALUMNI’ VISIT TO ST. ANDREWSThe post features a black-and-white shot of the Prince of Wales holding a then-baby William, as well as his son sitting alongside the proud patriarch and his stepmother, Camilla, Duchess of Cornwall.The British royal family’s official Twitter account also shared several photos of a smiling William from over the years.”Wishing The Duke of Cambridge a very Happy Birthday today! #HappyBirthdayHRH,” the post read.William thanked the public on social media for the well-wishes.CLICK HERE TO SIGN UP FOR THE ENTERTAINMENT NEWSLETTER”Thank you for all the birthday wishes and kind messages,” William wrote on the official Duke and Duchess of Cambridge Instagram page.On Sunday, William celebrated Father’s Day by kicking off a half-marathon at Queen Elizabeth II’s Sandringham Estate alongside George and Charlotte, PEOPLE magazine reported.The trio was dressed casually for the event as they cheered on all the runners.William has two more special birthdays coming up in his calendar. On July 1, he is expected to join his younger brother, Prince Harry, to unveil a new statue dedicated to their late mother Princess Diana, who would have turned 60 that day. Then on July 22, his eldest son George will celebrate his eighth birthday.CLICK HERE TO GET THE FOX NEWS APPWilliam is second in line to the British throne after his father. Over the years, William has taken on numerous charitable activities, projects and official duties in support of his grandmother the queen.In May, William and Middleton, 39, launched their YouTube channel where they chronicle their duties as senior members of the royal family. The Associated Press contributed to this report.