Christians: please help me..!?

He may be your biological brother, but he(as of now) is not your brother in Christ. You are not wrong to feel hurt, anger, or even feel taken advantage of by his actions- I think we all would. Even if your parents won't punish him, try to talk to them about how it makes you feel; and even how you feel how he's taking advantage of them as well. I read an article today relating to what you are experiencing so I'll give you a link. I'll pray that your brother will find the glory that is Christ; even if he never finds Christ, you should never lose your faith, no matter what! Peace of Christ be with you!