I have a mum and her two kittens (now 5 months old) that we got from a local cat rescue (not Cat Proection).
They were described as semi-feral and had just arrived the day before. The mum was v affectionate with humans but v feisty around other cats. The kittens seemed nervous of being handled. We picked them up two weeks later once they were over 8 wks old and the rescue felt they were ready to go.
They hadn't had much handling and we had to take baby steps to get them to interact with us rather than their mum, but 3 months down the line they are fab. The little girl still hates to be picked up but all three will sit with you/on you/across you, follow,you round the house, come to,greet you, play etc whilst still being a tight family group.
We googled the lack of interaction and got over it like this-had to offer a finger tip for them to sniff (looks like a cat nose) then progressed to stroking side of their faces, then sides of the body then full body strokes. I also picked each of them up briefly before feeding them and put them down before they started struggling (about three seconds with the little girl!) and played regularly with them - chasing a pencil across my lap whilst on the floor got them used to me as an obstacle, but a safe one.
Although the little girl doesn't like being picked up she adores being stroked, especially on her tummy, so she totally trusts us. Kittens are fun. Don't let them out too soon either. Only mum goes out for now, the other two we're leaving another couple of months.