Many 'experts' state that kittens must be handled by humans before they are 5 weeks old if they are to be social cat. Personally I think as long as they are not hurt or scared by humans you have until they are at least 12 weeks old, if not longer. Of course unless they are born where they can be observed constantly, it's difficult to know just what has happened to them. My neighbor's tom brought a pregnant feral (about 6 months old, non-vocal, very shy) to me to feed, when the kittens were about 8 weeks old she brought them close to my house, then she started going inside to eat. I finally was able to get her and all 3 kittens in the house and started working with them. The 2 orange males were very shy and they took a lot of patience, the dilute tortie has yet to meet a stranger and was friendly from the first. I believe their Mama had been cared for when she was young, I can't prove it, but she did become a very friendly, non-vocal, inside cat. All of them became friendlier after they were fixed, the most skittish...well it took him 2 years before he would climb on a lap. For treats and wet food, he had to tolerate being touched, we had to watch that there were no sudden moves, no loud voices and he eventually began to trust.