I'm thinking of keeping my friend's cat
Why are you thinking of keeping your friend's cat?
I feel like I'm the cat's only hope.
It's wrong to try and steal animals from a friend. You should at least ask him if it's okay.
My friend is 8 years old and he's a child. He doesn't want to take care of the cat.
So, it sounds like the best thing to do is talk it over with him. If he doesn't want the cat, he'll tell you and then there is no reason to steal it.