Earl Spencer, the younger brother of Princess Diana, joined the Duke of Cambridge and the Duke of Sussex at the long-awaited statue unveiling, which took place on Thursday at the Sunken Garden in Kensington Palace.
Following the family reunion at the private ceremony, Charles, 57, took to Twitter to share two photos, along with the caption: "Today, in Kensington. A good day."
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Both Prince William and Prince Harry were seen warmly greeting Charles and his two older sisters Lady Jane Fellowes and Lady Sarah McCorquodale, who were among a handful of guests invited to the unveiling of Diana's statue, on what would have been her 60th birthday.
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They happily chatted away when they first arrived, walking into the immaculate garden together ahead of the brief ceremony. The appearance has marked the first time the relatives have seen each other since Harry's move to America with his wife Meghan.
Charles Spencer tweeted these pictures after the intimate ceremony
The aunts and uncle have remained close with William and Harry since their mother's death in 1997. They all attended Harry's eldest child Archie's christening in 2019.
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Last month, Charles was quizzed about the public row over the name of Prince Harry and Meghan's newborn daughter, Lilibet Diana Mountbatten Windsor.
Prince Harry and Prince William greeting their aunts and uncle on Thursday
Speaking on ITV's Lorraine, the 9th Earl Spencer said: "When I look at all these newspapers going berserk again and I've always found it so hard, I think it's because I'm not very imaginative, but I always see things in terms of family.
"And I remember when I was a boy and Diana became Princess of Wales, I just sort of ploughed along on the same path. You separate the media personality from the real person who's a member of your family, and that's all that matters at the end of the day."
Princess Diana's siblings have remained close with the royal brothers
The couple's lawyers have written to the BBC after a story claimed the Queen had not been asked about naming their baby Lilibet, which was the monarch's childhood family nickname. But it had been widely reported that the couple did consult with Her Majesty Queen before the name of their baby, who was born in California on 4 June, was announced.
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