Ha, he just came home, and he says the idea that they're out there does unnerve him slightly. :D

You just need one child and I think anyone else, I know it definitely works with adults.

I'm probably not patient enough to wait for it, usually my sims have a very tight toddler-training schedule so there's no time for them to sit around in the crib. :P Do they have to know how to walk to do it, or is that one of those spaghetti-twins type myths?