He was Count of Ponthieu, ruler of a small province in northern France that fell under the suzerainty of the dukes of Normandy (later also kings of England) since at least the mid 11th century.
William was the son of John I, Count of Ponthieu and Beatrice de St Pol.
[2] William also participated in the Albigensian Crusade, particularly in the siege of Termes in 1210, where he and the count of Dreux informed Simon de Montfort they had fulfilled their indulgences and were departing the siege.
[3] William was married on 20 August 1195 to Alys, Countess of Vexin, the daughter of King Louis VII of France.
[5] Richard sent her back to her brother, King Philip II of France, refusing to marry her.