King Cadell Ddyrnllug's son, Cyngen the Renowned, is probably to be identified with the Aurelius Caninus denounced by Gildas in his late 6th century tract, De Excidio Brianniae. This name is a rather bad punning insult that means 'dog-like'. Gildas accused Aurelius-Cyngen of immorality and murder and causing civil war in Britain. Later generations, however, appear to have only remembered his patronage of the saints and generous endowments to the Church.

Cyngen married St. Tudlwystl, a daughter of Brychan ap Gwyngwen ap Tewdr (often confused with King Brychan Brycheiniog) and they were parents of a large family: Brochfael Ysgithrog, Cadell, Ieuaf, Maig Myngfras, Mawn and Sanan. What could be his memorial stone was discovered being used as a gatepost at Tywyn in 1761, but this is in Gwynedd. The inscription suggests he may have been buried with St. Cadfan in the local churchyard.