The death of Rhodri is given as 754. If Hywel succeeded at once, it would give him, dying in 825, a reign of seventy-one years, which seems unlikely. In 813 the Annales Cambriae reports him fighting with a brother, Cynan, for control of Anglesey. Cynan gained possession in 816 but died later the same year. Cynan's daughter, Ethyllt, was the mother of Merfyn Frych and founded a new line of Gwynedd kings.
From The Kings and Queens of Britain in Oxford Reference.
Subjects: British History.