Here's what to do:
First, get in touch with the sister and apologize to her for how you conducted yourself and that you didn't really know what was going on because you were so drunk. Make sure to take note of the exact date and time that the call was placed.
Secondly, when/if the brother approaches you, flat out tell him that if he touches you that you'll charge him. If he does, charge him. I'm absolutely sure that when you tell him that you're going to file charges against him if he touches you, that he'll have a change of heart.
Most importantly, if he does proceed to beat on you, make sure to take in the surroundings. Remember any witnesses around you. Also take note of the conversations that you've had over the past little while, remembering dates/times and key points in the discussions you've had.
I can't understand the rationale to want to intentionally hurt someone. When I was in grade 5, I got the hell beaten out of me. I wasn't liked because I was the fat kid that nobody hung with, so I always stayed to myself. One Monday in May, the principal came into our classroom and told us that one of our classmates was in an auto accident, and that she and the rest of her family had died. The one guy who really hated me for whatever reason started spreading lies that I was laughing about it. Well, when I was going home that night, he and about 20 other people were waiting for me. I had broken ribs, they kicked me in the face with those boot-styled shoes that were the rage back then, I couldn't see out of my left eye, broke my left arm, and cracked my right wrist. I pulled myself up to the wall when they left, and just sat there for what seemed like an eternity. A girl that lives down my street found me after her volleyball practice, and went to get a teacher. I left before they got back, and when I got home, I have my mother and father's faces engraved in my soul. They rushed me to the emergency room to get me taken care of. I know that they went into the school the next day, and the parents of the children that I did know were called in, but we never pressed charges.
I've never fought anyone since this, because I remember how I felt. I would never wish the hurt on anyone, so I try to be diplomatic about everything. Violence solves nothing.
