I don't really know how to title this so sorry if the title is vague. Basically I have household that is on it's 3rd, going on 4th generation in SV but the file size of my game is getting too large that I'm experiencing annoying lags. So I'm planning to move them into a new SV game. But the thing is, if I move them into a new game, then the rest of the town will be 1st generation original townies. I'm specially concerned about the University part because one of the sims in this household married a UL townie so it'll be weird when their grandkid gets to Uni and he goes to class with another version of his grandmother. They have some similar traits so I'm sure I'd get that pop up about them wanting to get to know each other better.
So my question is, is there a way to adjust the generation of the population in a new game so that it's at more or less the same level as my household?
One thing I thought of is to play the new game passively for a while until the town ages. Like I'll pick a random household then set the lifespan to short and just let it run in fast forward until the original townies die. But then it would still incur some file space which is just counterproductive. Is there a better way to do this?