A tenth-century genealogy in the British Library (Harley MS 3859) identifies him as the grandson of Coel Hen, and ancestor of Morcant Bulc.
[4] His family was a cadet branch of the dynasty of Brutus, the dominant line having ended with Porrex I before the civil war.
The Book of Baglan expands on this by making Dyfnwal descend directly through the male line of Camber via his eldest son, Gorbonian.
Following the defeat of the rival kings, Dyfnwal created a crown like that of his predecessors and claimed the throne of Britain.
[6] He reigned in peace and prosperity for forty years then died and was buried in the Temple of Concord, a tribute to his laws, which resided in Trinovantum.