Gruffydd ap Gwenwynwyn

When Llywelyn ap Gruffudd increased his power in Wales after 1255, Gruffydd continued to support the crown, and in 1257, he was again driven into exile.

Dafydd was with Llywelyn at the time, and it was arranged that Owain would come with armed men on 2 February to carry out the assassination; however he was prevented by a snowstorm.

There have been suggestions that his eldest son Owain may have been involved in the killing of Llywelyn at Cilmeri in December that year.

For his loyalty to Edward I, the king permitted Baron de la Pole to begin building (or re-building) Powis Castle.

Owain divided the lands he inherited with his brothers, by arrangements later recorded in detail in the Calendar of Patent Rolls for 1342, pages 496–7.