I haven't looked in Mabkor's history specifically, but from my experience it goes something like this:
* You either bring in people or you talk to the "abstract" ones already in town and make them historical figures.
* Those people make no children, die of old age or leave.
* They usually leave for two reasons: either they're travelers (some AI seem to have that coded into them, up to the point it's almost a glitch; most of those are scholars by the way, I think Avolition, Kesperan and Unraveller have unleashed the most of those who just won't sit in one place and spam a location's entry until they die one way or another) or the game gives them group rulership titles. The game does this because it's too lazy to make new historical figures for those rulership titles.
* This is how, by the way, the damn thralls spread so far and wide. An abstract unimportant number gets infected by an adventurer (say, Hannibal). Until then they either didn't exist more than abstract numbers or existed in some
quantum flux state. A historical creature who had a position in a group dies, and the game forces an existing historical figure (usually, but not always, from the same civilization) into that position. Cue blighted thralls in all populated places of the world.
Well, there's no harm in trying. Maybe something great will come of it. It's an interesting mechanic to explore, if nothing else.