My brother and I share a two bedroom apartment. I do drink somtimes but never do any drugs. His girlfriend and him do weed and some meth on weekends. She is a knockout with a great body. She has a key to our apartment and is there a couple times a week. My brother went to the casino with friends and wasn't coming back til the next morning. I got home late and was slightly drunk. When I went in the apartment all the lights were on and knew I had turned them off. I looked in my brothers room thinking he came home early but it was his girlfriend. She was under the sheet and sound asleep but I could see parts of her side and knew she was naked and probably stoned. I turned out the light and went to bed. As I thought about her I got a hard on and went back in my brothers room. It was pitch black and I shut the door and got in bed with her. I'm not sure what my intentions were but think I just wanted to feel her up, but I was naked and horny. She had rolled over and laying face down. I gently stroked her rear and back and felt the side of her breast. She put her hand on my hip and rolled to her side. I couldn't see her but now was able to feel her breasts. She turned over on her back and seemed to react to my touch. I stated to finger her and she held my penis for awhile and she leaned over and started kissing me. I'm sure she thought it was my brother. Now I was kissing her breasts and fingering her and I knew she was turned on and wet. We had sex for the next half hour and it was probably the best I ever had. She constanly touched me and french kissed me. We just held each other for awhile and she asked me to get her a glass of water. I got up and snuck out the door and brought back water to her not turning on any lights. I gave her the water and just said something like "bathroom" trying to sound like my brother. I went back to my room and didn't fall asleep for at least an hour dreading when my brother did come home. When he finds out what I did, he's going to kill me. I didn't wake up until almost 10am and started to worry all over again. I went to the bathroom but heard the shower running. I had to pee so bad I went in the kitchen sink. I went over to my brothers room and he was in bed asleep. When his girlfriend came out of the bathroom she had a towel wrapped around her. I expected her to start screaming at me but she just waved and went back in my brothers room. I still sat nervously and when she came out and into the kitchen she just asked if I made coffee. Somehow I got away with it and she never said a word about it. She thought she had sex with my brother and I don't know what time he came home. She hung around awhile and kept looking to see if my brother was awake. The whole time I was shaking and waiting for her to realize what I did. When she left, she just told me to have my brother call her. He never got out of bed until 2 in the afternoon and I knew right away she never said anything to him and wondered if he had sex with her also when he came home. I've seen her 5 more times since then and am convinced she doesn't know it was me. It was a dumb thing to do but I still dream about it and masturbate thinking of it. I know my brother and if he ever found out there would be hell to pay. I am sorry for my brothers sake but get hard everytime I think about her.