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
William, Duke of Brunswick the ruling duke permanently. William left most government business to his ministers, and he spent most of his time outside of his state at his possessions in Oels. While William joined the Prussian-led North German Confederation in 1866, his relationship to Prussia was strained, since Prussia refused to recognize Ernest Augustus, Crown Prince of Hanover, his nearest male-line relative, as his heir, because of the Duke of Cumberland's claim to the throne of Hanover. William died in 1884; he passed on his private possessions to the Duke of Cumberland. His death caused a constitutional crisis for Brunswick that lasted until