A new member of the family?

Monday night Chris picked the kids up from Margie's after work. As he was there, he found one of the freaking cutest little kittens we've ever seen wandering around outside in the freezing cold. He didn't tell me, but he decided to bring it home for just the night so we could play with it & love it. I think something might be wrong with it's stomach because the cat is like a furry balloon with 4 legs attached to it, its belly is swollen to about twice the size it should be. The kitten is really super cute & playful with both of the kids, which is great because Frenchie can barely stand to even be in the same room as anyone but me. She usually only likes to coming out when she can have me all to herself. Or when she needs to beg for food. She doesn't like having another cat in the house, but she was the same way with Gucci, and they quickly became best friends & slept together every night. When Chris came home he announced that he wanted to keep the kitten, but apparantly Margie's neighbor came over today & asked if she had seen the baby cat anywhere, it was their's. We honestly don't feel like they deserve to have the cat back after they left it outside in freezing temps & there is obviously something wrong with it & needs to be looked at by a vet. Pretty much the rest of the family agreed but we haven't decided what to do yet. What do you think?