He was the son of Madog by the daughter of the Maer du or "black mayor" of Rûg in Edeyrnion. Presumably Owain Brogyntyn would have been raised by his mother at Rûg in Edeyrnion. He was acknowledged by his father and granted by him the lordship of Edeyrnion and also Dinmael.
He was the brother of Gruffydd Maelor the ancestor of Owain Glyndŵr. At some point he also came into possession of Castle Brogyntyn on the English borders at Selattyn close to Oswestry. In 1160 after the death of his father and his eldest half-brother, he inherited a share of the Kingdom of Powys.
Owain first married Jonet verch Hywel (whose ancestor was Athelstan Glodrudd of the Fifth Royal Tribe) but with her had no children.
The son of Iorwerth and Efa, Gruffudd ab Iorwerth, was confirmed in his lands as Baron of Edeyrnion by Edward I under the terms of the Statute of Rhuddlan by which England organised the subjugation of Wales. According to Philip York writing in 1799 a cup and a dagger belonging to Owain Brogyntyn were preserved at Rûg in Edeyrnion.
Later accounts in the National Gazetteer dated 1868 state that a cup and dagger in the possession of "Colonel Vaughan of Rhug" were once owned by another Owain of Powys, the much later Owain Glyndŵr. These objects, whoever the original owner, may now be lost.
The direct patrilineal descendants of Iorwerth ab Owain Brogyntyn survived at least until the beginning of the 20th century and are known to genealogy as the Hughes of Gwerclas family.
