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.
William Ernest, Duke of Saxe-Weimar William Ernest, Duke of Saxe-Weimar William Ernest, Duke of Saxe-Weimar (19 October 1662 – 26 August 1728) was a duke of Saxe-Weimar. He was born in Weimar, the eldest son of Johann Ernst II, Duke of Saxe-Weimar and Princess Christine Elisabeth of Schleswig-Holstein-Sonderburg. When his father died in 1683, he succeeded him as duke; however, he was compelled to rule jointly with his younger brother Johann Ernst III. Because John Ernest III was alcoholic, William Ernest took full control of the government of the duchy and permitted John Ernest the nominal title of co-duke ("Mitherr") until his death in 1707.