Mountbatten-Windsor – Wikipedia

Mountbatten-Windsor is the personal surname used by some of the male-line descendants of Queen Elizabeth II and Prince Philip, Duke of Edinburgh.Under a declaration made in Privy Council in 1960, the name Mountbatten-Windsor applies to male-line descendants of the Queen without royal styles and titles. Individuals with royal styles do not usually use a surname, but some descendants of the …

https://en.wikipedia.org/wiki/Mountbatten-Windsor