Letting Her Younger Sister Watch
When I was 17 I was often over the house of my 15 year old girlfriend and her 13 year old sister. When their Mom was working my girlfriend and I would get into some serious kissing, touching and feeling, usually in front if the TV with her younger sister present. My girlfriend never seemed to mind that her sister was there and she once told me her sister had a crush on me. One day, while my girlfriend was asleep in her bedroom I told her younger sister that I was going to join my girlfriend and that she could watch us a few feet away in the doorway but she had to be quiet. She just nodded and when I got into bed with my girlfriend I pulled off her shorts and panties and pulled her shirt up to her head, leaving it so that it covered her head and face. My girlfriend liked to be forced to submit like this so she didn't stop me when I spread her legs and pulled her butt up as she knelt. I quickly was completely out of my clothes kneeling behind her and entering her from the back. I made sure to bang her ass hard as I f***** her in her p**** and my girlfriend was pretty loud herself. What she didn't know was that her younger sister was standing just 3 feet away watching us have hard s**. I kept looking back at her sister every time I moaned "I want you so bad" and I motioned with my hand for her to rub herself, which she did through her shorts. The younger sister came quickly as soon as she started rubbing her p**** and seeing that I came hard, moaning loadly, as I came inside my girlfriend "I love you" as I looked directly at her wasted sister. My girlfriend never found out about this. It was the best s** I ever had.