A complicated character, William is by turns extremely brutal (the Harrying of the North which Edith refers to) and quite generous in his forgiveness of enemies.  He really did forgive Morcar and put him into exile in Normandy.  He was also happily married to Mathilda, with whom he had nine children, but he would severely punish anyone that mentioned his status as a batard, or bastard.  He was a hard man but a successful ruler, overall.