In the struggle for the English Crown between Stephen and Mathilda, Geoffrey de Mandeville has been described as ‘the typical figure…perpetually changing sides and perpetually raising the price of his allegiance’. He was the grandson and heir of a follower of the Conqueror of the same name, which being latinized occurs as de Magnavilla or de Magnaville. ‘The elder Geoffrey appears in Domesday as a considerable tenant-in-chief, his estates lying in no less than eleven different counties’, though none in Somerset. He had a son and heir William who was constable of the Tower and the father of the Geoffrey of Stephen's time who became first earl of Essex and died in 1144. The latter's two sons, another Geoffrey and another William, became second and third earls, dying respectively in 1166 and 1189.

It has been stated that, in addition to William, the elder Geoffrey, companion in arms of the Conqueror, had other sons, Geoffrey (II) and Roger, the former of whom held the barony or honour of Marshwood in Dorset of the king in capite and the latter succeeded to his father's estates in Normandy, which would have made them uncles of the first earl of Essex. This relationship is not, however, very definitely established and the de Mandevilles of the west, though they were doubtless of Norman origin and of the same stock as the Geoffrey of Domesday Book, may not have been directly descended from him.