List of Famous people with last name Cynfyn

Bleddyn ap Cynfyn, sometimes spelled Blethyn, was an 11th-century Welsh king. Harold Godwinson and Tostig Godwinson installed him and his brother, Rhiwallon, as the co-rulers of Gwynedd on his father's death in 1063, during their destruction of the kingdom of Bleddyn's half-brother, Gruffydd ap Llywelyn. He became king of Powys and co-ruler of the Kingdom of Powys with his brother Rhiwallon from 1063 to 1075. His descendants continued to rule Powys as the House of Mathrafal.

Rhiwallon ap Cynfyn was an 11th-century Welsh King and co-ruler of the kingdoms of Gwynedd and Powys from 1063 to 1070. The son of Cynfyn ap Gwerstan and brother of King Bleddyn of Powys. Through his mother Angharad, he was half-brother to King Gruffydd ap Llywelyn as well. Following the 1063 invasion of Wales by Harold and Tostig Godwinson that overthrew Gruffydd, Rhiwallon and Bleddyn jointly received Powys and Gwynedd on condition of faithfully serving Edward the Confessor "everywhere by water and by land".