They're growing up so fast! Prince William looked like he was having a great Father's Day with Prince George, 7, and Princess Charlotte, 6, on Sunday, June 20.
The trio were spotted at Queen Elizabeth's Sandringham Estate, where they helped cheer on runners who were participating in a half-marathon.
In photos obtained by PEOPLE, the 39-year-old wore a button-down shirt with dark pants, while George sported a plaid long-sleeve shirt with shorts and Charlotte donned a pink long-sleeve shirt with blue shorts.
The two tots helped their dad start the race, which is organized by Good Running Events. William was also photographed holding George's hand.
Kate Middleton and Prince Louis, 3, were not in attendance.
Royal fanatics were so surprised to see how tall George and Charlotte are.
"One year later, George and Charlotte are so big," one person said.
Another added: "Crikey, they have shot up."
"George is going to be taller than his father at this rate, and that's saying something”, a third person said.
The Duke and Duchess also took to their Instagram account to share a sweet message on the special day.
"Wishing fathers everywhere a happy Father’s Day," they captioned a video, which showed some never-before-seen photos of the royal family.
One photo was of Kate with her father, Michael Middleton, on her wedding day, and another showed William smiling with his three tots, which was from a previous Trooping the Colour event.
Of course, people couldn't get enough of the snapshots. One person wrote, "The trooping photo is so adorable 😍," while another added, "Please release that picture with prince William and the kids..it's so sweet😭😭."
A third user added, "That new picture on the bottom left is so beautiful!!! We need it in HQ 🥺🥺😍😍😍 happy father's day to our Duke of Cambridge, to Prince Charles and to Michael Middleton! Amazing dads ❤️❤️❤️❤️."