You can add toddlers, kids, and teens or anyone to anyone in Manage Households. They will grow old by themselves. (if you have aging on for Non played Sims). I have added husbands, wives, kids etc. But remember the more you add the more that may get culled. So delete any Sims in the bin (Manange Households) you don't want in your game. There is a population cap then the game starts culling/deleting Non played Sim in the game. But it culls anyway every Sunday.