 In Jesus College MS 18, Selyf is identified as father of Beli and subsequently ancestor of the later kings of Powys; in other genealogies, he is father of an Eiludd ap Selyf, and in another, he is identified as grandfather of a Beli ap Mael Myngan ap Selyf.Breneu Powys, or the Privileges of Powys, by Cynddelw Brydydd Mawr, the court poet of the major Kingdoms of Wales at the time, refers to Selyf's descendants as serpents of battle, most likely in reference to the Mathrafal dynasty, which ruled Powys at the time.This suggests that Eiludd, who is most commonly identified as progenitor of the continuation of the House of Gwerthrynion, was likely to have been a son of Selyf.