Not knowing a lot about your family dynamics I am reluctant to make any suggestions. I can tell you what I did.
Around your brothers age I started with stating I no longer wanted to attend church, I wasn't getting anything out of it. They then forcefully stated that I was going to church and didn't have a choice. So I went. About 10 minutes into the service I got up and walked out. They weren't willing to make a scene in church or any where near in case other church people might be watching. Fortunately I lived in a small town and was able to walk home. When they got home there was a bit of a lively discussion and then silence (my family's way of dealing with uncomfortable situations was silence). The next Sunday the same thing, went, then walked out. It must have sank in for them over the course of the two weeks because I was only asked to attend church after that, not forced. They gave me the choice. With time the atheist discussion came up but it was not a heated discussion. I stated my position that I should be able to believe or not believe what I chose just as they were. They were able to accept that and it was never an issue again.
Around your brothers age I started with stating I no longer wanted to attend church, I wasn't getting anything out of it. They then forcefully stated that I was going to church and didn't have a choice. So I went. About 10 minutes into the service I got up and walked out. They weren't willing to make a scene in church or any where near in case other church people might be watching. Fortunately I lived in a small town and was able to walk home. When they got home there was a bit of a lively discussion and then silence (my family's way of dealing with uncomfortable situations was silence). The next Sunday the same thing, went, then walked out. It must have sank in for them over the course of the two weeks because I was only asked to attend church after that, not forced. They gave me the choice. With time the atheist discussion came up but it was not a heated discussion. I stated my position that I should be able to believe or not believe what I chose just as they were. They were able to accept that and it was never an issue again.
Being told you're delusional does not necessarily mean you're mental.
