Anonymous. When I was 30, I had a nanny job that was at least 10 hours a day, plus I would spend up to 3 hours a day commuting, sometimes more. It almost killed me and I was tired all the time and honestly, I was not a great nanny to this family because of it.
Therefore, Mountbatten-Windsor is the surname of all male (and unmarried female) descendants of Prince Philip and Queen Elizabeth II; this includes Prince Charles, Prince William and Prince Harry. Because Prince Harry and Price William use the title Prince, they do not use the last name Mountbatten-Windsor. They use the surname Wales because they are the sons of the Prince of Wales. Although Royals don't tend to use a last name, in the instance of a marriage, for example, Prince William's last name is Mountbatten-Windsor. This is the surname of all descendants of Prince Philip and Queen Elizabeth II (excluding females who marry).
Now that the titles thing is all cleared up, let's talk about that last name. Prince Harry's full name is actually Henry Charles Albert David Windsor. Yeah, it's a lot. When Kate Middleton married Prince William, she took his last name of Windsor, so it's expected that Meghan Markle will become Meghan Windsor as well. All of these confusing name and title changes will take place during the royal wedding, which the royal family announced on Monday morning will take place in the spring of 2018.