Catherine, Duchess of Cambridge, Prince William, Duke of Cambridge, Princess Charlotte of Cambridge and Prince George of Cambridge talk to Queen Elizabeth II, Prince Phillip, Duke of Cambridge and Camilla, Duchess of Cornwall arrive at the Church of St Mary Magdalene on the Sandringham Estate for the Christening of Princess Charlotte of Cambridge on July 5, 2015 in King's Lynn, England.
The royal baby‘s surname is unclear at this point, but it could be Mountbatten-Windsor. Prince William and Duchess Catherine typically don’t use the surname, because of the titles before their first names. George V in 1917 declared that Windsor …
therphmqueen: 'Royal Family' for the National Portrait Gallery 2000 by John Wonnacott-Queen Elizabeth the Queen Mother surrounded by Prince William, Prince Harry, Prince of Wales, Queen Elizabeth, Duke of Edinburgh and corgis
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According to BBC News, the royal baby's last name could be Wales, like dad; Cambridge, the title given to the couple when they married; or Mountbatten-Windsor, the surname of Prince Philip, who got Mountbatten from his maternal grandparents, and the queen, whose father, King George V, selected Windsor for his family in 1917.