If you go into Manage World, then Manage Households, and choose Unplayed, you can see all the townies the game has generated (it says Not Currently In World). I also think the game generates townies based on the household you created. My single sim adopted a child, and when I went to look at the townies, there were an awful lot of families with a single parent and a child, whereas other games I have had hardly any children townies. As townies tend to disappear, if I find ones I like, I will move them into a lot so they stay in the game. If there's a lack of children or teens, I often make a household with a few kids so that my sims kids have someone to hang out with.