William the Conqueror eldest son. William was the son of the unmarried Robert I, Duke of Normandy, by Robert's mistress Herleva. His illegitimate status and his youth caused some difficulties for him after he succeeded his father, as did the anarchy that plagued the first years of his rule. During his childhood and adolescence, members of the Norman aristocracy battled each other, both for control of the child duke and for their own ends. In 1047 William was able to quash a rebellion and begin to establish his authority over the duchy, a process that was not complete until about 1060. His marriage
Guy, Duke of Sorrento forever loyal to the Hauteville leadership, however. In 1073, he captured the rebel Herman, his own nephew, and handed him over to Robert Guiscard, his nephew-in-law. Guy died amidst the breakup of the great principality his brother had forged and he had preserved. With his death, Sorrento became independent once more. His children were: Guy, Duke of Sorrento Guy (; born c. 1012) was the duke of Sorrento from 1035, the brother of Guaimar IV of Salerno, father-in-law of William Iron Arm and William of the Principate, and brother-in-law of Humphrey of Hauteville. He was the son of Guaimar III