Oh, that is sad. I kinda sense from your posts that there's a little tension between your parents and you right now. If it were otherwise, I'd just say take the cat. But your relationship with your parents should probably come first. I would gradually work on getting them to realize what they are doing. Maybe printing up some neat, concsise easy to read info and suggesting they read it. I don't know, really tough situation, but the health of this cat is very important in general and obviously to you. I'd say take slow little steps, and do it as kindly and rationally as possible. (Even though it sounds like that's what you are already doing).