I only want to play my main sim but eventually want her to get married and have a kid. I heard that you can make toddlers in households NPCs, does that carry into when they grow up into children and teens and yound adult, etc.? And is there any possible way to make a spouse in the household a NPC? (Not just ignoring it)?
I /think/ you can go to the "Edit Town" option in the Options Menu, and you can move sims to different households. I had an adult NPC move in with my main Sim, but then wanted to move her out again, and "Edit Town" is how I did it. I'm not completely sure if it'll work on toddlers, though. --- War does not determine who is right, only who is left.