Almost all versions of the Arthurian story have Owain as Urien's son and Arthur's nephew, and the later accounts assume his mother is Morgan le Fay, if not one of the King's other half-sisters. He has a half brother called Owain (or Yvain) the Bastard after him, the product of a union between Urien and his senechal's wife. The Welsh give him a twin sister, Morvydd, and as Arthur's maternal nephew he is a cousin to Gawain and the Orkney clan.