This happened to me not to long ago with my current girlfriend when we  went and visited her sister and mom. Kerri is a tall blond with c cup  tits and light brown nipples... I had seen them on vacation when her top  was loose. She has an average figure and nice butt. One of the nights  we were staying we all were talking and playing card when we decided to  call it a night and go to bed. Kerri's boyfriend ed was over that night.  I had woken up and was feeling thirsty it was really late close to 3 AM  and my water tasted old so I went downstairs to get some water from the  cooler. I stepped slowly and quietly because my girlfriends mothers  room is right next to the stairs. When I got downstairs I saw that the  TV was left on but no one was there so I went into the kitchen and  started to get my water when I heard some noise. I quietly opened the  door to the basement and the noise got louder and leaned over once I  realized what the noise was and I saw Kerri on top of her boyfriend  riding reverse cowgirl. I could not see much because Kerri still had her  top on but I could see her pussy and her boyfriend balls smacking her  cunt. She looked hot but I got there late because she quickly pulled out  and got on her knees and took his load on her face. She sucked on him  for a longer but I decided to leave before they had a chance to notice..  That was the only time iv gotten the chance to see her sister in  action.. I'd probably fuck her if I had the chance.