Here is the story. My wifes younger sister is smoking hot. When I she is smoking hot, I am not exagerating. She is a part time model and a cosmotology student with Paul Mitchell. She is 20, about 5'8" and weighs about 120 pounds. She has long brunette hair, sky blue eyes, and about D sized fake boobs. She also has a great fashion sense. I am 25, 6 foot, 160 pounds, pretty well muscled (many of my female friends have told me that I am attractive). Before my wife and I got married we had a great sex life. I was young and had just joined the Army. She was cute as hell. When we would go to her mom's house, during the summer we were dating, we would hang out by the pool. Of course I was showing off for my soon to be wife's benefit by walking around with out a shirt. I think my wife's sister was checking out the goods. I was 21 at the time. My sister in law would flirt with me and liked to hang out around me. I didn't think much of it. After a few years of marriage and a couple kids, my wife has lost all drive to have sex and is over weight. I was about to deploy to Afghanistan and we were visiting my mother in law. My wife and mother in law took the kids to the park for the day. I stayed back to catch up on some sleep. My sister in law had been out late and was sleeping in as well. I had gotten up to take a shower. When I was walking out, I was only wearing a towel. My sister in law was waiting for the shower next. As I was heading to the guest room, she told me that I had a great body and that I was really hot. I told her that I thought she was really pretty. She advised me that she didn't mean that I was just good looking, that she was sexually attracted to me. I smiled at her and went into the guest room. Apparently she followed me in. She was only wearing a towel and so was I. I was getting a great look at her curves. I started to get aroused and she noticed. She let her towel fall to the floor and took mine off. I hadn't had sex in over a year, so I was definitely not thinking in the right mind or I would have stopped her. She went down on me until a climaxed in her mouth. She swallowed it, picked up her towel and told me that was a thank you for being so nice to her and walked out. I pushed the encounter to the back of my mind and tried to forget about it. Unfortunately she is really hot and every time I see her, I can't help but remember. Lately I have found my self wanting to have sex with her. Is it normal?