[2][3] Enguerrand was married to Adelaide, daughter of Robert I, Duke of Normandy and sister of William the Conqueror.
[2][4] But at the Council of Reims in 1049, when the proposed marriage of Duke William with Matilda of Flanders was prohibited based on consanguinity, so was Enguerrand's existing marriage to Adelaide, causing him to be excommunicated.
[10] Duke William had put Arques under siege, but had remained mobile with another force in the countryside nearby.
[11] To relieve the siege Enguerrand was with Henry I of France and on October 25, 1053 was killed when the Normans feigned a retreat in which Enguerrand and his companions followed and were ambushed, a tactic the Normans used again to great success at the Battle of Hastings.
[a][12] By her he had a daughter: As Enguerrand died without male issue[13] he was followed by his brother Guy I as Count of Ponthieu.