Welcome to PC calla75 and sorry you experienced all this drama. I don't know whether your brother has a personality disorder, but his actions are inappropriate. Your friend also acted very wrong for having sex on your couch, when she's a married woman and for letting your brother stay at her house. They imposed their actions on you by becoming intimate in your house. You don't have to tolerate him yelling at you or the hateful emails. He may be your brother by blood, but he's not acting like one.

You may have projected your own wishful thinking of how you thought he would be, but he's not really acting nice. If he can't give you respect, then he shouldn't speak to you until he can. They both took advantage of your hospitality.