He married Ankaret, daughter of Rhys ap GRUFFYDD, prince of South Wales, but in 1191 Rhys, contrary to his oath, expelled William from the castle of Nevern, giving it to his own son Griffin; later another son, Maelgwn, held it under Llewelyn. He died in 1208 or 1209, when William his son and heir owed 300 marks as relief. His widow died in or shortly before August 1226. [Complete Peerage VIII:532, (transcribed by Dave Utzinger)]