Prince William and Kate Middleton are like Madonna or Prince — despite their fame, no one knows their last name.
Okay, we all know “Middleton” — but what is Kate Middleton’s married last name? What is the royal family’s last name?
Technically, Kate Middleton no longer has a last name. As “Her Royal Highness the Duchess of Cambridge,” she belongs to the British people. She does not have a last name, and is simply — and officially — named “Catherine, Duchess of Cambridge.”
The same is true for Prince William. In school, he was enrolled as “Prince William of Wales,” “William of Wales,” or, quite simply, “William Wales.” Like Catherine, he belongs to the British people and does not have a last name.
However, if you had to put your finger on a last name, it would be Mountbatten-Windsor. That is the line — the Windsor clan in particular — that the ruling royal family descended from.