The Angevin kings of England (the line of rulers to which Henry II belonged), were Philip's most powerful and dangerous vassals as Dukes of Normandy and Aquitaine and Counts of Anjou. Philip made it his life's work to destroy Angevin power in France. One of his most effective tools was to befriend all of Henry's sons and use them to foment rebellion against their father. He maintained friendships with Henry the Young King and Geoffrey II until their deaths. Indeed, at the funeral of Geoffrey, he was so overcome with grief that he had to be forcibly restrained from casting himself into the grave. He broke off his friendships with Henry's other sons Richard and John as each acceded to the English throne.