92 camaro rs 25th anniversary edition?? help!?

So I have a 92 camaro rs 25 anniversary edition, and it won't start. I inherited it from my brother. It worked up to the day he left for bootcamp. But his stepmom told me she messed with it so nobody could drive it. But she's a b***h and we don't talk to her. By other brother has replaced the starter and tried 6 different batteries with it but it still won't start. Any ideas what could be wrong with it?