Duke of Normandy as the reign of William II (1035–87), the ruler of Normandy could style himself "prince and duke, count of Normandy" as if unsure what his title should be. The literal Latin equivalent of "Duke of Normandy", "dux Normanniae", was in use by 1066, but it did not supplant "dux Normannorum" until the Angevin period (1144–1204), at a time when Norman identity was fading. Richard I experimented with the title "marquis" ("marchio") as early as 966, when it was also used in a diploma of King Lothair. Richard II occasionally used it, but he seems to have preferred the title duke.
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