You think you know the British royals, but are you a true Anglophile? Do you know, for example, Prince Charles‘ full name? OK, that’s a trick question: Charles’ name is hard to pin down. The Prince of Wales, eldest child of Queen Elizabeth, was born Charles Philip Arthur George… but because he was born into British royalty, he doesn’t technically have a last name. Legally, British royals don’t need a last name.

When a surname is required, though, the descendants of Queen Elizabeth and Prince Philip often use the surname Mountbatten-Windsor, as Charles’ siblings Prince Andrew and Princess Anne did on their marriage registries. Charles’ son Prince William adopted Mountbatten-Windsor as his last name when he filed a lawsuit over topless photos of his wife, Kate Middleton. And Charles’ niece Lady Louise, daughter of Prince Edward, also uses Mountbatten-Windsor — since she’s the first descendant to not receive a “His/Her Royal Highness” designation.

Sometimes, however, the family uses their house names. For example, William and Prince Harry have used Wales as their surnames in their careers so far, Vogue has reported. William is the Duke of Cambridge now, and his son, Prince George, is already using Cambridge as his last name while at school.

Then again, Charles will be king one day, and then William will take his father’s title as Prince of Wales, and George will have to decide which name to use at that point. #RoyalFamilyProblems, right?

On top of royal fans being curious about everyone in the royal family’s full names, they’re most recently fixed on finding out William and Kate’s newborn son’s first name, — and they’re also very curious about his last name as well. Royal historian Marlene Eilers recently told Town and Country magazine, “The royal baby will not have a last name. The name on the birth certificate will say HRH Prince or Princess, and all three names of Cambridge.” We guess we’ll have to wait and see!

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