Need Help with Stray Cat in Distress

If you, or your sister or if your parents are up to it, have Facebook, look for a local rescue group. My city has a few that are just groups of people that work together to help strays. If it's fearful of people, a TNR(trap neuter release) group might be the most helpful, usually they'll trap or catch it, give it whatever veterinary care it need to be healthy again, then spay neuter and vaccinations. If by that point it hasn't warmed up to being around people they release it back where it was found so it can have it's happiest possible life. If it has warmed up to being around people they can find a foster or find it a home. But yeah definitely look into what resources you have in your area, outside of shelters. But if you can't find anything better and he looks sick calling your local animal control may be the best option. You can probably Google animal control [your city/area] to find there number, and read their website if they have one it will talk about what happens to the animals in their care. Feel free to message me if you'd like. I helped with some tnr and foster groups and used to volunteer with my cities main animal shelter

This is a really tough situation. If you can't catch the cat yourself and you're worried something bad might happen to it, call the local animal shelter. Reporting a stray animal won't put the responsibility of paying for its costs on you. If you can't take care of the cat as your own pet, taking it to a kill shelter stull might be better than allowing it to stay outside and in danger. Shelters often give animals they take in vet treatments. Your parents seem like they don't understand how stressful this is for you and that's ok-- just do what you can but don't beat yourself up for not being able to give this animal a safe home because, like you said, you are only 15.