 His son Gwenwynwyn ("ob".1216) took over lordship of the abbey and increased its endowments; 45 charters, many from the Wynnstay Estate Archives, survive in the National Library of Wales and elsewhere recording such benefactions to the Abbey, and it became a religious house of wealth and importance.Owain's son Gruffyd ap Gwenwynwyn, lord of Powys, entered a monastery when he was close to death about 1260, but recovered during his stay; it is thought that this abbey was Strata Marcella, which was near his seat at Pool.