his father became king of the french in 1830. this made the prince the heir to the title of duke of orléans and heir to the throne. from that time the heir to the french throne was to be known as the duke of orléans. his father also declared his descendants through the male line were entitled to use the style of "royal highness". they also used the title (a title in its own right) of prince of orléans. the prince became known as his royal highness, prince ferdinand philippe of orléans, duke of orléans. his sons were also entitled to the same style and title.