What do you guys think his race is? I think it's most likely that he was born to Atmorans who traveled to Highrock and then went to Skyrim to study with the Greybeards. This would solve the problem that he is very Nord-like, but isn't a Nord and came to Tamriel before the modern races were even around. He also ended up in Cyrodiil because it's the center of Tamriel, thus making it easier to rule the Empire, which also accounts for his descendants being Imperials.
If you want to know my sources, it's the fact that he was born before the Nords, Bretons, Redguards, and Imperials were around.