He was a grandson of Cadell ab Einion ab Owain ab Hywel Dda, and a great-grandson of Einon ab Owain, thus a descendant of Hywel Dda, king of the Britons. He married Gwladys ferch Rhiwallon daughter of Rhiwallon ap Cynfyn of the Mathrafal dynasty of Powys, by whom he had four sons, Gruffudd, Hywel ap Rhys, Goronwy and Cadwgan, and a daughter Nest (who married Gerald de Windsor Constable of Pembroke, progenitors of the FitzGerald and de Barry dynasties of Ireland. These celebrated Hiberno-Norman, or Cambro-Norman, families have been Peers of Ireland since at least the 14th century.