We live near a wooded area, someone had evidently dropped off a kitten and he lived for about 3 months on his own. We would see him in the woods and try to get him to come to us. Eventually we couldn't find him until about 4 months ago he started to come to our drive way and moan and meow. He was skin and bones. I would put out food, but he would run away. Finally my other cat would meow to him and push food towards him and the little cat would come and eat. He is the sweetest cat and he has gained so much weight! :) We named him MoMo because he purrs so loudly and has such a loud meow. He was wild but such a sweet cat now, the children love him.
"I would put out food, but he would run away."
Your cat was smart enough to realize the kitten would die without something to eat.
Tuna, with a loud fish smell, is what I have used to coax several feral kittens and cats to eat. Once they start eating then I give them regular cat food. For inside kittens a plastic seal ring from a milk carton is a perfect toy. You can teach them to fetch in a very short time.
I have a livestock barn that is a magnet for unwanted cats and kittens. Must be the meeses that live there.