Posted 06 January 2019 - 20:39
Actually, the last name of the Royal Family is more complicated. Queen Victoria asked her advisors what her name was. They concluded her family name was Wettin and the name of the house was Saxe Coburg and Gotha. Later due to the war, both were changed to Windsor, in perpetually. When Princess Elizabeth married Philip, she took his name. Only after she ascended to throne, did she become a Windsor. This raised the question of the name for the children. Not only did Prince Philip want his name, but a legal expert pointed out that children who take their mother's name are usually illegitimate. Thus, by compromise some members of the family could go by Windsor-Mountbatten. I forget what the limitation is, but I think it is great grand children of the sovereign. This is the same limitation placed on the inheritance of both the style HRH and the title of Prince. It is possible for therefore a Windsor-Mountbatten to be a Duke though. This will most likely be the case with the Duke of Sussex's descendants.
However, to say that the Duchess of Sussex is called Meghan Windsor-Mountbatten is wrong. Meghan Windsor is probably in some sense correct, but I doubt her ID says that. Here is where it gets real complicated, all the people entitled to the style of Prince, either have a title like Duke or Earl or are styled Prince X of Y, with Y being the title of their father. For example, Prince Harry's military uniform before he was made a duke read Wales, and not Windsor.
The fact that the British media is clueless about this, is probably related to the fact that they are hacks and cyptorepublicans.