I use MC Command Center. I think these are the most important things I've changed affecting the repopulation. Obviously you can change around other things like there being chance for sims to be in a same-sex relationship. Unfortunately, the townies will only have babies (adoption or biological, depends on how you change the settings) or get married (so, no proposals or girlfriends, just marriage)
MCCC > MC Pregnancy > Marriage Sim Selection > Marriage Percentage
(I set it to 10% so townies wouldn't constantly be getting pregnant)
MCCC > MC Pregnancy > Marriage Sim Selection > Marriage Percentage
I also have this set to 10% because I don't necessarily want people getting married all the time either.
Obviously the townies won't breed to have like 20 babies unless you change the settings (default limit is 3 children per household)
I also have made it so they only marry and have babies with sims within the same age group (so young adults won't end up having babies with elders) with these commands:
MCCC > MC Pregnancy > Partner Sim Selection > Use Same Age Group
MCCC > MC Pregnancy > Spouse Sim Selection > Use Same Age Group