There is absolutely NOTHING wrong with you. It takes a mature person to acknowledge and accept their sexuality. And as for your younger brother, it is impossible to "turn him gay" as your parents suggest. I am not sure that convincing them you can be straight is the best idea, but if you want to stay at your school, you may have to be a really good actor until you turn 18.
You know what I think, I think Christian people have problems, They are so controlling and think everything you do is a sin if it’s what God “didn’t want” So I guess I’m saying your parents have problems there is absolutely nothing wrong with you.