My brother fucked my girlfriend

I'm 17 and my brother is 14. My brother is an athletic kid, captain of the school basketball team and he spends 2 hours a day after school at the gym. He's also a straight A student and class president. Tall, good looking, muscular, good with girls. He got his first girlfriend when he was 11 and he has a very healthy sex life, mostly with older girls. I've never been athletic at all and I'm still a virgin, but I recently got my first girlfriend. We were dating for 3 weeks and we hadn't done anything beyond kissing, and last weekend I brought her over to my house for the first time. My dad was out and I thought my brother was going to spend the night at one of his girlfriends places, but it turns out he stayed home.

Things were going good with my girlfriend and we were watching a movie on the couch and holding hands, but then my brother came downstairs shirtless and sweaty after working out. He took notice of my girlfriend and talked to her for a bit, she was staring at his bare chest the whole time and it made me uncomfortable. Then my brother started doing pull-ups in the door frame and my girlfriend was staring at him the whole time, not watching the movie at all anymore. My brother got on the couch in between us (shoving me aside a bit) and turned to my girlfriend, and they started chatting flirtatiously. She asked about how much he works out and he offered to let her feel his muscles, she actually squealed when he flexed his bicep and she spent a long time running her hands over his abs and pecs. She was practically drooling and he was hitting on her pretty openly.

She went to go to the bathroom leaving me and my brother alone for a bit, and I asked my brother if he could please go back upstairs, I was practically begging him to not take my girlfriend as we both know he could. I never expected what he did next, in the middle of my sentence he lowered his sweat pants and revealed his big soft dick. Then he ordered me to do the same, and when I hesitated he flexed his bicep at me threateningly and I obeyed. The size difference between us was huge, and as I looked I felt mine hardening up. I guess it was from the humiliation, but it also felt like a submissive gesture, like there was a little white flag of surrender attached to my dick that was being hauled up as it rose. Now I was fully hard and my brother was still soft, but his dick was still significantly bigger than mine. I know mine is 4 inches hard, his must have been about 5.5 soft. Finally he broke the silence by saying "you thought you were going to fuck her with that little thing?" I looked down at the floor but he took my face in his hand and forced me to look. He asked "which of us is the man here, and which is the boy?" I mumbled "you're the man, I'm the boy". He said "good, so pull your pants up, be a good boy and go to your room". We both pulled our pants back up and I got up to leave, which was when my girlfriend returned to the room. My brother said "It's past his bedtime now, but you and I can stay up". She didn't question it at all, in fact she looked delighted, and she ran back to the couch to sit next to him again. I went upstairs and tried to get some sleep. An hour later I got thirsty and went downstairs for some water when I saw her on her knees in front of the couch, slobbering over his huge cock. They moved on to other things afterward and I hardly got any sleep that night, they were extremely loud. The three of us had breakfast together the next morning and she's been coming over almost every day for the last week, mostly ignoring me and going straight to my brother's room.