Royals Happy 99th Birthday, Grandpa! Prince William and Kate Middleton Lead Tributes to Prince Philip The Duke and Duchess of Cambridge shared sweet photos in honor of Prince Philip's 99th birthday By Simon Perry Published on June 10, 2020 08:10 AM Share Tweet Pin Email Happy birthday, Prince Philip! On Wednesday, Kate Middleton and Prince William celebrated Philip's 99th birthday with a series of special photos. Sharing the photo gallery on their Kensington Royal Instagram, the first photo featured a smiling Kate standing with Philip as he waves, while the second photo showed a joyous moment between William and his grandpa — the two sharply dressed as they laugh together. "Wishing a very happy 99th Birthday to The Duke of Edinburgh!" they wrote, using his royal title. Queen Elizabeth and Prince Philip at Windsor Castle. Steve Parsons/PA Prince Charles honored his father's milestone birthday with two father-son photos posted on the Clarence House Instagram. A black-and-white photo featuring Philip taking a young Charles for a boat ride was the first photo displayed in the series, with the second image capturing a present-day moment between the duo while warmly chatting. Prince William Has Been Volunteering for a Crisis Text Line During Lockdown Princess Eugenie celebrated the occasion with a series of photos, leading with a portrait from her Oct. 2018 wedding. "A very Happy 99th Birthday to HRH The Duke of Edinburgh," she wrote. "Grandpa, we wish you a special day.. and may all grandparents celebrating birthdays in lockdown have a wonderful time." A sweet tribute also came from the Queen and the royal family's official Instagram account. A series of special photos, starting with a shot of the longtime couple with a baby Prince Charles, was posted alongside the caption, "🎈🎂Wishing The Duke of Edinburgh a very happy birthday! His Royal Highness turns 99 today and will spend the day with The Queen at Windsor." William and Kate are likely to join Charles, 71, Prince Harry, 35, Meghan Markle, 38, and their son, Archie, 1, along with other royals in making a series of phone, or video, calls to Philip as he spends the day alongside wife Queen Elizabeth at Windsor Castle. Philip is expected to be keeping the festivities low-key and will mark the day with a private lunch with the Queen at the Castle, where the couple has been in lockdown since March 19. Queen Elizabeth and Prince Philip at Windsor Castle. Steve Parsons/PA How Queen Elizabeth Is Keeping Calm & Carrying On at 94: 'She Has Impeccable Judgment' The series of birthday tributes come one day after Buckingham Palace unveiled a new portrait of Philip alongside Queen Elizabeth which was taken on June 1 at Windsor Castle. In the photo, Philip proudly wears his tie of the Household Division — the seven British army regiments that serve the Queen. He appears robust and "on good form," according to a royal insider. The Queen, who turned 94 in April, wears a cheerful blue and yellow floral dress by her dresser and close confidante Angela Kelly. She accessorized her outfit with a unique brooch, which carries the 18.8-carat Cullinan V diamond at its heart. Can't get enough of PEOPLE's Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more! On Saturday, the Queen will have an official, and relatively low-key, late celebration for her April birthday. She is to be serenaded at a military parade by some members of the Welsh Guards, led by Lt. Col. Henry Llewellyn-Ush.