The Aurelian family had a large role in King Arthur’s time and over previous centuries. It began in the 270s. K.O. Morgan, writing in the Oxford Mini-History of Britain, vol 1, said “In 274, Britain was brought back under the [Roman] central government when the Emperor Aurelian eliminated the Gallic Empire.” (‘The Gallic Empire’ was Iberia, Gaul, Britain, and the part of Germany west of the Rhine which had separated and been independently ruled.)
The link from Emperor Aurelian to the British Aurelians is the ancient reference* to a fifth-century leader called Ambrosius as a man “whose father wore the purple”. Only Roman Emperors were said to have “worn the purple”; but the word ‘father’ can be heard as meaning ‘forefather’.
This Ambrosius is the rival whom Vortigern defeated, according to a record included in the Historia Brittonum, at the Battle of Wallop in 428.
You could say he was walloped. However, another reference there is to Vortigern restraining his ambitions from “fear of Ambrosius”. So evidently he was walloped only partially. I have said in another post that Vortigern was de-facto Governor of Maxima Caesariensis, the Roman Province comprising south-east England. Wallop was in the Winchester civitas and quite close to the Province’s border with the western province called Britannia Prima. I reckon this Ambrosius may well have been Governor of Britannia Prima in the second quarter of the fifth century.
But what has this to do with the Aurelian name? The answer is that his son is known to history, thanks to Gildas, as Ambrosius Aurelianus. His floruit was around 480. In legend, this second Ambrosius is described as “the boy without a father” – obviously because his father, the first Ambrosius, was dead, most likely having been killed in battle; equally obviously, a fatherless boy who stood out from the crowd of such boys by virtue of his aristocratic lineage. This Aurelian Ambrosius is known in Celtic stories as Emrys Wledig: Emrys being his Celtic name that was Latinised to Ambros (+ the grammatical ending ‘ius’); ‘Wledig’ being a title denoting a great ruler. Perhaps he too was Governor of Britannia Prima…. though the distribution of Ambros-derived place-names suggests he may have carried the fight against Saxon raiders/invaders well to the east. John Morris’s map, on page 101 of “The Age of Arthur” (2001 edition), shows five such places in Britannia Prima – but eleven in Maxima Caesariensis, seven of them in or just outside Essex in a cluster suggesting that Ambrosius held a frontier to keep the Saxons of Essex out of ‘Calchfynydd’, the Kingdom whose name means ‘Chalk Hills’ centred on the chalk hills now called The Chilterns. **
Two later Aurelians are known to have been prominent. One is King Cynan Aurelian of Powys, who ruled that large kingdom in the west Midlands and mid-Wales in the early-middle part of the sixth century. He is known both from a Taliesin poem praising his warrior achievements and from a section of Gildas’s diatribe which attacks him as grossly degenerated morally from his illustrious grandfather Ambrosius Aurelianus. The other is St. Pol Aurelian, a contemporary of King Arthur, who was the benefactor who commissioned the strengthening of the old wattle church (the vetusta ecclesia) of Glastonbury Abbey with wood, and who worked as a Christian leader in Brittany.
* I think it’s in the Historia Brittonum.
** There is also one Ambros- placename in Oxfordshire, which was not in Maxima Caesariensis in Roman times. But this place had probably been acquired by the Silchester civitas soon after Ambrosius Aurelianus’s time by Cerdic, the governor/king who, as I have shown in my post on Cerdic, made conquests in Oxfordshire in c500CE to secure the left bank of the Thames for his kingdom which already included a large stretch of the right bank.