Kate Middleton, along with her children Prince George, 12, Princess Charlotte, 11, and Prince Louis, 8, shared a heartfelt tribute to William on Instagram in honor of his special day. This celebration took place on Sunday, June 21, coinciding with Father's Day in both the United States and the United Kingdom.On Father's Day, Kate Middleton and her children honored Prince William by posting a cherished photo on Instagram.The family chose to share a previously unseen photograph of Prince William holding Charlotte in the gardens of Kensington Palace, taken after their return from Trooping the Colour on June 13."Happy birthday and Father's Day to the best Papa in the World! We love you very much. C, G, C & L 💕," the post read.Prince William attended Trooping the Colour with Kate and kidsThe tributes follow the official royal appearance of Prince William, Kate Middleton, and their children at Trooping the Colour last weekend, which is the British Army's celebration of King Charles' official birthday.During the procession, Prince William rode on horseback, while his wife and children were transported in a horse-drawn carriage through London. Afterward, they convened on the balcony of Buckingham Palace to observe the flypast that concludes the festivities.The Prince of Wales is next in line to the throne after his father, King Charles. Despite the significant responsibilities that await him, he disclosed last year that his foremost priority is his family.During the show, the heir to the throne mentioned that 2024 was the most challenging year of his life, as both his wife and father dealt with cancer. In early 2025, Princess Kate announced that she is in remission, while the King's treatment is still ongoing."I'd say 2024 was the hardest year that I've ever had," William had stated. “Trying to sort of balance protecting the children, Catherine, my father needs a bit of protection, but he's, you know, he's old enough to do that himself as well.”"But it's important that my family feels protected and has the space to process a lot of the stuff that's gone on last year, and that was tricky trying to do that and keep doing the job. But you know, we all have challenges that come our way, and it's important to keep going."