Weused to foster kittens for Thundering Paws Animal Sanctuary, a no-kill shelter near us. They were usually kittens rescued from feral cat colonies. Some had no previous interaction with humans, and needed to be taught to trust people. It takes a lot of time and patience, but it's always fun to have kittens for a few weeks. The hard part is letting them move on when they are old enough and socialized enough to be adopted. You'd think that would get easier with time, but it really didn't so we don't foster any more.