Caracthers of Alice Eve and Cumberbatch = canon.
Eve - Dra. Carol Marcus
Cumberbatch - Garth of Izar
He is starship captain.
He can be younger than the original. After all, this is a diferent time line.
Only characters born after Nero's arrival/Kirk's birth, the point that the timelines split can be different in age. (Chekov). Garth was already a famous Captain when OldKirk was at the Academy. Garth has to be ten to twenty years older than Kirk, probably closer to Pike's age.