Latin: Flavius Claudius Constantinus
Died before September 18, 411
He is also known as Constantine II of Britain and is confused with Geoffrey of Monmouth’s Constantine, found in Historia Regum Britanniae. Geoffrey’s Constantine becomes the grandfather of Arthur, through his son Uther Pendragon. Some sources claims that Constantine III is the grandfather of Arthur. The Welsh Triads tells us that Arthur’s grandfather is “Custennin the Blessed”, also “Bran son of Dyfnwal and Custennin son of Elen had been emperors in Rome”.
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138
Triads of the Island of Britain (Welsh ”Triads”) | 11th century to 14th century