How do I get my kitty back?

A few years 以前 I got my first cat and I named him Sam. I had never had a pet that wasn't a family pet 或者 that belonged to my sister, so Sam is very important to me, I 爱情 him so much.

I have some neighbors, and they seem to like to feed the neighborhood 猫 human 食物 and let them come into their house.... Once when my family was gone and Sam was wandering around the neighborhood, they must have let him come into their house, and they wouldn't stop, so 你 know what that ended in? Sam basically living there, and not coming home.
This same thing happened with my other cat Speck, after about a half a 年 passed, we basically gave up with trying to get her back. Turns out, these people gave Speck to someone else without asking us, and once Speck started living there she got sick, turns out she had stomach cancer, and they had to put her down, they didn't tell us until my mom gave in and tried to get Speck back.

These people are very nice, and I really want to like them, but I can't, I just can't. Sam occasionally comes onto our back porch, and he runs away if I get to close to him. I have to call him for a few minutes, and then he comes over and snuggles me, but he won't come in. Soon after that, he runs away to go back to my neighbors' house. I'm seriously crying right now, I can't take it, it just makes me so angry.

I really miss Sam, and I want him home, but I want him to be happy and not me just trapping him in the house. Is there any way I can get him to actually want to come home? Please.