NPC and Babies

MC Command Center can do that for you, although there's no guarantee it will be those people who will marry, have kids, etc. At least as far as I know. Someone more experienced might be able to help, but figured I'd chime in with my little bit of info.

Or you can just go to manage worlds and add a spouse and make the babies in CAS

I can link the mod if you want, but I use pregnancy mega mod that allows me to choose any sim to get impregnated by any other sim without having to play that sim. It has been a lifesaver in keeping my game populated.

I absolutely hate hate hate how toddlers in TS4 ps4 randomly gain tons of weight! It gets really annoying when you're doing everything right and out of nowhere they gain weight. Toddlers metabolism is all jacked up

Sims 4 has no story progression so this is impossible without mods, or without playing all the different households to make sure they get kids as well. In sims 3 NPCs would get married, have children and careers etc, without you having to interfere, but this was removed for some reason.

However, in my experience MC command will fix ALL of this. If you want a certain sim to have kids, you can click them and mark them for "marriage", which will make them marry a randomized sim in the next marriage cycle, and after that they will usually get kids as well. It works pretty much like the story progression in the sims 3.

I have avoided modding for years (thinking it would be hard to do and buggy) but I eventually realised that MC command was essential to my gameplay, and i was pleasantly surprised to learn that it was really easy to install mods for the sims.