Did King Louis 14th really have a twin brother Phillipe The man in the Iron Mask?

Besides the movie, it's true that there was a real "man in the iron mask" and is even mentioned in the Memoirs of Mme du Barry. He is disputed to be either the Duc de Vermandois, a twin brother of Louis XIV, or an elder brother of Louis XIV. However, it should be noted that the "Iron Mask" wasn't an iron mask at all. It was a simple mask of black velvet.