In British law, a commoner's someone who's neither the Sovereign nor a peer. Therefore, any member of the Royal Family who isn't a peer, such as HRH Prince William of Wales or HRH The Princess Royal,'s a commoner, as's any member of a peer's family, including someone who holds only a courtesy title, such as the Earl of Arundel and Surrey (eldest son of the Duke of Norfolk) or Lady Victoria Hervey (a daughter of the 6th Marquess of Bristol). Traditionally, members of the House of Commons were co… (More on Commoners)