First off, I should explain I do not come from a Muslim family. While my father and mother are christian, my brother does not seem to be religious in any way (at least not outwardly). This story starts in December of last year, a few weeks after he started dating this girl. He told us that she was 18 and that she was about to graduate high school and all that. However, I started getting messages from some of his former friends, telling me that she was actually 16 years old. I was, at first, shocked but also not convinced. After all, these were his former friends, and I didn't know if they were just trying to start trouble.
Still, I confronted him, and he assured me they were lying. Still, I couldn't let it rest (while I love my brother dearly, I am sad to say he is not very trustworthy.) Turns out they were right. Some snooping on instagram revealed she was, indeed, only 16. And newly turned 16 at that. My first fear was the law, but where I live in the US the age of consent is 16. Next, my fears went to family. Legal or otherwise, if my parents found out they would be furious. He just got off probation and I didn't want to see him fall down again. So I confronted him again, and we had a deep, rather heated, discussion.
Long story short, I told him that as family I'd always have his back, but that I did not necessarily approve of the relationship. I thought that was the end of that.
However, today, one of his former friends started messaging me again, talking about how I was an "a-lister" and my brother a pedophile, and began posting things on Facebook. He didn't name any one, but it's very obvious. I'm not sure what to do, especially if this blows up in his face. I personally do not feel threatened by this guy, but I worry about my family back home.