Gaston, Duke of Orléans
He was originally known by the title "Duke of Anjou". In 1660, his paternal uncle, Gaston, Duke of Orléans, died. The dukedom of Orléans was an appanage traditionally conferred upon the younger brother of the French king whenever available. Philippe exchanged Anjou for Orléans. As a son of a French king, Philippe ranked as a "fils de France", and as the king's younger brother, he was invariably referred to at court simply as "Monsieur".