Complex sentence: Captain-General Royal Marines is a ceremonial rank, usually held by a member of the Royal Family.There is not a Field Marshal rank for the Royal Marines, although Royal Marine officers may reach full General rank.
Split into simpler sentences: Captain-General Royal Marines is a ceremonial rank, usually held by a member of the Royal Family. The role of Commandant General being held by a Major-General.There is not a Field Marshal rank for the Royal Marines, although Royal Marine officers may reach full General rank.