[6] William Longsword was born "overseas"[a][7] to the Viking Rollo (while he was still a pagan) and his wife more danico (a kind of non-Christian marriage), Poppa of Bayeux.

[b] According to the Longsword's planctus, William was baptized a Christian probably at the same time as his father,[15] which Orderic Vitalis stated was in 912, by Franco, Archbishop of Rouen.

[16] William succeeded Rollo (who continued to live about five more years) in 927[17] and, early in his reign, in 933, faced a rebellion from Normans[18] who felt he had become too Gallicised.

[27] In 935, William married Luitgarde,[1] daughter of Count Herbert II of Vermandois, whose dowry gave him the lands of Longueville, Coudres and Illiers-l'Évêque.

[21] He also contracted a marriage between his sister Adela (whose Norse name was Gerloc) and William, Count of Poitou, with the approval of France's most powerful magnate, Hugh the Great.

[29] In January 936, Raoul died and the 16-year-old Louis IV, who was living in exile in England, was persuaded by a promise of loyalty by William to return and became king.