Historic adversaries Henry III (d. 1272) and Simon de Montfort (d. 1265) were actually kin twice over. They were both great-great-great-grandchildren of William the Conqueror, each through the latter’s son Henry I. It was the legitimate line in Henry III’s case, illegitimate in Simon’s. They also had a common ancestor in the first Simon de Montfort, a French nobleman who like William the Conqueror died in 1087. It was legitimate in both cases, for Simon through son Amaury and for Henry through daughter Bertrade and her first husband Fulk of Anjou. They were the grandparents of King Henry II. This means that Simon and his wife Eleanor (Henry III’s sister) also shared the same, thick bloodline, hence their rough and rowdy brood of de Montfort children.