Taking to their social media accounts, Prince William and Kate shared a stunning photo of Meghan on Bondi Beach in Sydney during the Sussexes' tour of Australia in 2018, to mark her 40th birthday.
The caption read: "Wishing a happy 40th birthday to The Duchess of Sussex! [birthday cake emoji]."
WATCH: Kate Middleton quizzed about new niece Lilibet
Prince Harry and Meghan welcomed a new addition to their family in June, with the birth of their daughter, Lilibet Diana Mountbatten-Windsor.
Kate was asked about her new niece as she carried out a joint engagement with US First Lady, Dr Jill Biden, at a school in Cornwall during the G7 Summit in June.
"I wish her all the very best. I can't wait to meet her," replied Kate. "We haven't met yet. I hope that will be soon."
The Cambridges posted a photo of Meghan during her Australia tour
It's not unusual that the line of succession on the royal family's website isn't updated straight after a birth. Similarly, it was almost two months before Princess Eugenie's son, August, was added to the website after he was born in February.
William and Harry were reunited at Princess Diana's statue unveiling in July
The Cambridges were last seen publicly with the Sussexes at the Commonwealth Day service at Westminster Abbey in March 2020, shortly before Harry and Meghan moved to the US after stepping back from royal duties.
Prince Harry was reunited with his brother and sister-in-law at the Duke of Edinburgh's funeral in April, where they were spotted walking together after the moving service.
The Duke of Sussex was also reunited with his older brother, William, to unveil a statue of their late mother, Diana, Princess of Wales, at Kensington Palace in July.
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