HYWEL ap RHODRI MOLWYNOG From http://wbo.llgc.org.uk/en/s-HYWE-RHO-0825.html

(d. 825 ), king of Gwynedd ; a great-grandson of Cadwaladr (d. 664 ) (q.v.) , and the last king in Anglesey of the line of Cunedda (q.v.) . The blood of Cunedda was transmitted, on Hywel 's death, to a new royal house through his niece, Ethyllt (grandmother of Rhodri the Great ) (q.v. ), daughter of his brother, Cynan (d. 816 ), with whom he had for long contested Anglesey .

Bibliography:

■A History of Wales Author: Professor Thomas Jones Pierce, M.A., F.S.A., (1905-1964), Aberystwyth.

Darrell Wolcott has shown that the Hywel of Rhos, who was never King of Gwynedd, was acyually Hywel ap Caradog, Caradog being the interim king of Gwynedd who was killed by the Saxons in 798:

Please see Darrell Wolcott: Cynan Dindaethwy - Furter Notes; http://www.ancientwalesstudies.org/id307.html (Steven Ferry, October 21, 2022.)