Alan IV, Duke of Brittany of William the Bastard, Duke of Normandy (later to become known as William the Conqueror) support of rebels in Brittany against Alan's maternal uncle, Conan II. Conan II died in late 1066 during a campaign in Anjou, and was succeeded by Alan's parents, Conan's sister Hawise and her husband Hoel II. Hoel ruled as regent from Hawise's death in 1072 until Alan reached his majority in 1084. To prevent further hostilities during his invasion of England, William I married his daughter Constance to the new duke Alan in 1087. The marriage ceremonies may have taken place in Bayeux in Normandy.
William I, Duke of Bavaria William I, Duke of Bavaria William I, Duke of Bavaria-Straubing (Frankfurt am Main, 12 May 1330 – 15 April 1389, Le Quesnoy), was the second son of the emperor Louis IV the Bavarian from his second wife Margaret of Holland and Hainaut. He was also known as William V, Count of Holland, as William III, Count of Hainaut and as William IV, Count of Zeeland. In 1345 William's father was conferring Hainaut, Holland, Zeeland and Friesland upon his wife Margaret, and shortly later also upon their son William. After his father's death in 1347 William ruled Bavaria, Holland and Hainaut