William FitzAlan, the son and heir of William by Isabel, who succeeded as a minor and apparently came of age in 1175. He married a daughter of Hugh de Lacy, Lord of Meath [Rot. Hundredorum, vol.2, pp.69, 76, 80, referring to land given to William FitzAlan with the sister of Walter de Lacy, cited by Eyton, vol.5, p.86, vol.10, p.126] and died in 1210 [Eyton, vol.7, p.244 citing the Annals of Dunstable Priory; since printed in Annales Monastici, vol.3 (Rolls Series no 36; 1866)].