Some genealogies (namely Ancestors of Paul Mcbride on the internet) have John the son of Gilbert FitzRichard de Clare, 2nd Earl of Clare (1066-1114) & Adelaide de Clermont.
John Mareschall, attaching himself to the fortunes of Maud against King Stephen, was with Robert, the consul, Earl of Gloucester, at the siege of Winchester Castle, when the party of the empress sustained so signal a defeat. Upon the accession of Henry II, however, in 1154, his fidelity was amply rewarded by considerable grants in the co. Wilts; and in the 10th of that monarch's reign, being then marshal, he laid claim, for the crown, to one of the manors of the see of Canterbury from the prelate, Thomas + Becket, who about that period, had commenced his contest with the king. To this John s. his son and heir, John Mareschall. [Sir Bernard Burke, Dormant, Abeyant, Forfeited, and Extinct Peerages, Burke's Peerage, Ltd., London, 1883, p. 357, Marshal, Barons Marshal]