Girlfriend and sister

One day while over my girlfriends house ( now wife ), we were sitting on the couch fooling around. Nobody was home, but we were always causious cause people could come in at any time. She locked the door and we started getting a little more into it. I had her 38EE breast out ( see photos ) and was licking her nipples. My balls were hanging like a pair of beagles ears and she was playing with them. I started playing with her pussy. I would rub her clit and slide a finger or two in. After I made her cum, she got on her knees and started blowing me. She would lick the shaft and suck on my balls. I sat back with my eyes closed, and enjoyed every stroke, lick and flick of my cock and balls. After a good 10 mins of steady head, I shoved my cock down her throat and spewed my load. Just as I was getting ready to get up and clean up, we heard someone coming in the back door. She threw a blanket over my still pulsing hard cock. Her sister walked into the room and said hi. My girlfriend then said with a mouth full of cum "HELWO" ( she did'nt swallow at that time ). Her sister the blanket pointed up. She came over and ripped it off my lap. Without a blink of her eye, she grabbed my cock and slid her hand up and down a few times. She then licked the dribbles of cum off her hand. Just as if nothing had happened, she turned around and went up stairs. Now every time my sister-in-law sees me, she just smiles and licks her lips.