William the Conqueror
In 1083 Queen Matilda died and was buried in Caen. The two had been very close and only disagreed over their son Robert Curthose. Robert had repeatedly rebelled against his father yet kept in contact with his mother. This caused a rift between them. Philip I of France had found it difficult for his vassal to become a king like himself and so resented William. Not strong enough to fight William himself, when Robert Curthose rebelled against his father, King Philip helped him.