Ambrosius Aurelianus
Uther's family is based on some historical figures; Constantine on the historical Constantine III, an usurper claimant to the Roman throne from 407 to 411, and Constans on his son. Aurelius Ambrosius is Ambrosius Aurelianus, mentioned by Gildas, though his connection to Constantine and Constans is unrecorded. It is possible that Uther himself is based at least partially on Tewdrig, a historical king of Glywysing in the sixth century, given the strong similarities between their death stories.