William was son of Robert II of Bellême and Agnes of Ponthieu. He succeeded his father as count of Ponthieu some time between 1105 and 1111, when he alone as count made a gift to the abbey of Cluny. His father Robert de Bellême had turned against Henry I on several occasions, had escaped capture at the battle of Tinchebrai in 1106 commanding Duke Robert"s rear guard and later, while serving as envoy for King Louis of France, he was arrested by Henry I and imprisoned for life.
He was seigneur de Montgomery in Normandy and Count of Ponthieu. William was naturally driven by this to oppose King Henry. In June of 1119, however, Henry I restored all his father"s lands in Normandy.
In 1135 Henry I again confiscated all his Norman lands to which William responded by joining count Geoffrey of Anjou in his invasion of Normandy after Henry I"s death 1115, Helie of Burgundy, daughter of Eudes I, Duke of Burgundy.
Europäische Stammtafeln, however, shows eleven. The five both agree on are: Guy World War II He assumed the county of Ponthieu during his father Talvas" lifetime, but died in 1147 predeceasing his father.
William, Count of Alençon. John I, Count of Alençon, married Beatrix d"Anjou, daughter of Elias II, Count of Maine and Philippa, daughter of Rotrou III, Count of Perche.
Clemence married (abt 1189) Juhel, son of Walter of Mayenne.
Adela (aka Ela) married William de Warenne, 3rd Earl of Surrey.
