[3] From childhood, he harboured a bitter dislike for his cousin Henry I of England,[a] and proudly demanded from him not only his father's earldoms of Mortain and Cornwall, but his uncle Odo, Bishop of Bayeux's Earldom of Kent.
"[4] The king kept putting off William's demands for the earldom of Kent and instead offered him the hand of Mary of Scotland, Queen Matilda's sister, which William promptly rejected.
[4] Henry in turn gave her in marriage to Eustace III, Count of Boulogne.
[4] Henry then removed lands in Cornwall from William he had allegedly misappropriated, after which William angrily left for Normandy joining forces with Robert Curthose.
[5] He was captured with Duke Robert at the Battle of Tinchebrai (1106) and stripped of Mortain.