He is married to Lleucu verch-Iestyn van Glamorgan.
Eineon (fl 1093), Welsh prince and warrior, son of Collwyn, played a great part in the famous legend of the conquest of Glamorgan by the Normans. His father and his elder brother Cedivor seem to have been under-kings in succession of Dyved or of some part of it. In 1092 Cedivor died. His son Llewelyn and his brothers, his sons according to another account, rose in revolt against Rhys ap Tewdwr, the chief king of South Wales, but were overthrown by him at Llandydoch. These discords gave easy facilities to the Norman marchers to extend their conquests in Wales. Next year Rhys was slain by the French of Brecheiniog. The conquests of Dyved and Ceredigion immediately followed. Thus far the history is authentic, but Eineon's name does not specifically appear in it. The legend now begins. Eineon, the brother of Cedivor, fled from the triumph of Rhys at Llandydoch to Iestin, son of Gwrgan, prince of Morganwg, who was also a rebel against Rhys. NOe Eineon had been previously in England, he served the king in France and other lands, and knew well both William himself and his great barons. He proposed to Iestin to bring his Norman friends to the latter's help on condition of his receiving his wife the daughter of Iestin and as her protion of the lordship of Miscin. Iestin accepted the proposal. Einwon visited his English friends at London. He persmacded Robert Fitz-Hamon, whom we know in history as lord of the honour of Gloucester, and twelve other knights to bring a great army to the aid of Iestin, Rhys was slain by them in a terrible battle near the boundaries of Brecheiniog, at Hirwaun Gwrgan. With Rhys fell the kingdom of South Wales. The Normans, having done their work for Iestin, received their pay and returned towards London. They had hardly departed with Iestin, flushed with his triumph, treacherously refused Eineon his daughter's hand. Eineon pursued the retreating Frenchmen, explained to them his own wrongs and the general unpopularity of Iestin, and showed hos easy it would be for them to conquer Iestin's dominions, since his treason to Rhys had so much disgusted the South-Wales princes that not one would afford him succour. The Normans were easily persmacded. Eineon meanwhile organised a Welsh revold. They jointly spoiled Iestin and Morganwg, but the Normand took the rich vals for their own share and left Eineon only the mountains of Senghenydd and Miscin, while the sons of Iestin were rewarded for their acquiescence in their father's fate by the lowland lordship of Aberavon. Induced byt the victory of Fitz-Hamon, other Normans seized upon Dyved, Ceredigion, Brecheiniog. Thus the treachery of Eineon put all South Wales into the hands of the foreigner.
This full and elaborat story is first found in the 'Brut y Tywysogion,' first printed in the second volume of the 'Myvyrian Archaiology,' and afterwards with a translation by Mr Aneurin Owen for the Cambreian Archaeological Association in 1863. But the original manuscript of this 'Brut' is believed not to be older that the middle of the sixteenth century, and therefore not much earlier that Powel's 'History of Cambria' (1584), in which the story of the conquest of Glamorgan also appears at length, varying from the above account, in only a few details. There are here added, however, the long pedigrees of the descendants of the 'twelve knights,' and most critical inquirers have agreed that the fertile invention of the pedigree-makers for Glamorganshire families is the original source of the legend. But there must be some nucleus of trugh and some ancient basis for the inventors to have worked upon, for the conquest of Glamorgan is undoubtedly historical, though there is no direct account of it in any earlier authority. There is nothing in itself improbable in the story of Eineon, there there are slips in detail. If he had such great connections, why did his not use them to save his native Dyved from Rhy's assault? Rhys, too, was undoubtedly slain by Bernard of Neufmarche and the conquerors of Brechiniog. Moreover it is absurd to suppose that after doing their work the Normans would have gone home again or needed Eineon's suggestion to turn their attention to the conquest of Morganwg. Obviously the expansion of the Norman arms from Gloucester into Morganwg was as natural as that of the expansion of the Shrewsbury earldom into Powys. But the quarrels and invitaitons of local princes were here, as in Ireland, a determining cause of their action; and Eineon's part in the conquest is too probably and typical for us lightly to reject the whole of his history. Some Welsh families profess to be descended from Eineon. [Dictionary of National Biography VI:585-586]
Einion ap Collwyn (fl 1100?), according to tradition, quarrelled with Iestyn ap Gwrgant, and in consequence invited the Normans to invade Glamorgan. He is a semi-legendary figure, and it is significant that at least three different accounts of his descent are given us. According to one story, he was the son of Collwyn ap Gwaethfoed of Ceredigion; another makes him the son of Cadifor ap Collwyn of Dyfed; while poets like Lewis Glyn Cothi and Gwilym Tew, assert that he was a man of Gwynedd who migrated to Glamorgan in Iestyn's days - and George Own adds that his father Collwyn was nephew to Angharad daughter of Ednowain ap Bleddyn of Ardudwy and mother of Iestyn. It may be observed that Lloyd's Hist. W. ignores Einion completely, and that he had intended to exclude him from the present work. The traditions about Einion, about the gentle families of the Glamorgan uplands who claimed descent from him, and about his connections with the literary history of Glamorgan will be found conveniently recounted in G.J. Williams, 'Traddodiad Llenyddol Morgannwg,' 1948, indexed. [Dictionary of Welsh Biography p202]