Amhar, Amyr, Anir
According to Nennius and Welsh legend, Arthur had a son named Amr, though all he says of him is that Arthur killed him (without explanation) at Archenfield and that he was buried under a mound called Licat Anir in Ercing. Nennius claims to have visited the grave, which had the strange property of changing size, a property he says he personally checked out and verified.
In the Welsh story of Geraint, we learn that Amr served as his father's squire, guarding his bed.
Amr is probably identical with Amhar, son of Arthur mentioned in the Mabinogion. The form Amr is preferable to Anir, which is also found.
In Nennius' introduction to Chrétien's Yvain, Julian Harris recaps old, pre-Chrétien rumors of Arthur's son Amyr, or Anir, and his marvelous tomb. Amyr is apparently unkown to later romancers, at least under that name; one of the old legends Harris mentions has it that he was killed by Arthur himself, reminding us of the Vulgate's Lohot.
Borre | The Legend of King Arthur
Loholt | The Legend of King Arthur