I'm saying that because Jake does not go on to have kids in the Prime universe, there is no need for a Mirror Jake. If Jake did have kids, they would have MU doppelgangers*, which would require the existence of a Mirror Jake who also had kids. If parallel reproduction didn't exist, then the whole Mirror Universe phenomenon would quickly fall apart, if its existence was even possible in the first place.
(* Jake's kids would not have doppelgangers if they did not themselves reproduce.)
A broader explanation:
For the Prime and Mirror universes to be parallel (parallel planets, societies, individuals), despite infinite possibilities for divergence, it would require either the intervention of some intelligence, or else be the function of a natural law. In either case, we can theorise that, when individuals don't have duplicates in the other universe, this is because the system has deemed duplication unnecessary. If duplication is unnecessary, this suggests that the individual is not important to maintaining the parallel nature of the universe into the future, i.e. they don't do anything historically important and they don't have kids.
Y'get me?