The son of King Iago, he likely assumed the crown of Gwynedd around 615, shortly after the Battle of Caer-Legion (also known as Chester), during which the forces of Gwynedd were defeated by Æthelfrith of Bernicia. Despite Æthelfrith's military victories, Cadfan continued to provide haven for Edwin of Northumbria, whom Æthelfrith regarded as a major threat.
Cadfan was generally considered to have been a wise and just ruler, noted for his ability to maintain the rule of law and peace during an increasingly hostile period in British history. His memorial stone at Llangadwaladr Church in Anglesey refers to him as "Catamanus rex sapientisimus opinatisimus omnium regum" (="King Cadfan the wisest and most renowned of all kings"). He was succeeded by his son Cadwallon.
He was one of the last of the legendary kings of the Britons as accounted by Geoffrey of Monmouth.
(From Wikipedia, the free encyclopedia)
CADWAN was made Governor of the territory theretofore ruled by the Kings of the Britons and maintained honor and peace for, although a war with the Northumbrian Saxons was intended, yet by the mediation of friends a peace was concluded; died 635; married Acea, the divorced queen of Ethelred, King of Northumberland.
(Fenwick Allied Ancestry, page 180)