Unlike most male siblings in the UK, Prince William and Prince Harry's children do not share the same surname - something that is very surprising to many royal followers.
This point became even more of a talking point when the Duchess of Sussex gave birth to her first child last year.
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William and Kate's little ones – Prince George, Princess Charlotte and Prince Louis – all have the last name 'Cambridge', taking after their dad's title, the Duke of Cambridge.
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When the Duke and Duchess of Sussex's son was born on 6 May 2019, Buckingham Palace announced that the royal tot had not been issued with a title and would be known as Master Archie Harrison Mountbatten-Windsor - a nod to his great-grandparents, the Queen and the Duke of Edinburgh.
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Members of the royal family traditionally don't use a surname; they are simply known by their first name or title in the public eye, and His or Her Royal Highness.
Harry and Meghan with baby Archie on their royal tour of Africa
According to the royal family's official website, a declaration made by the Queen in Privy Council in 1960 said that male-line descendants of the monarch, without royal styles and titles, shall bear the name Mountbatten-Windsor.
This also reflects both of their last names and differentiates their direct descendants from the rest of the royal family.
The website adds: "Unless The Prince of Wales chooses to alter the present decisions when he becomes king, he will continue to be of the House of Windsor and his grandchildren will use the surname Mountbatten-Windsor."
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William and Harry grew up with the surname 'Wales', using it at school, at university and during their time in the army.
William was known as Lieutenant Wales while Harry had the rank of Captain Wales.
This is because their father Prince Charles' title is the Prince of Wales but following their marriages, William and Harry were granted new titles from their grandmother the Queen, and their children are expected to take these on.
Prince George, seven, is enrolled as George Cambridge at his school Thomas's Battersea, where his sister Princess Charlotte, five, started in the reception class last September and is therefore known as Charlotte Cambridge.
William and Kate's children all take the surname 'Cambridge', following their dad's title
In a similar vein, Princess Eugenie and Princess Beatrice also use the surname 'York' after their father Prince Andrew, the Duke of York.
William and Kate are proud parents to George, Charlotte and two-year-old Prince Louis.
The Duke and Duchess of Cambridge welcomed their third child in April 2018, just three weeks before attending Prince Harry and Meghan's wedding.
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Royal fans were delighted when the Sussexes announced they were expecting their first child on the first day of their royal tour of Australia in October 2018 and Archie Harrison was born on 6 May 2019.
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