sister walks in SeXStoRY

Back in high school my g********d at the time (wife now) and I had started having sex couple of months prior to this story. We were both *6 at the time she was half Mexican half white dark brown hair green eyes 5' 2'' she was a little thick but it looked great on her and to top it off she had 34d tits. Like most t**nagers we were horny but we were a little more active then most we would have sex at least twice a day. Her mom was out of town and her dad worked all day at his auto garage 6 days a week so we had plenty of time to have fun since it was summer time. This day we were hanging out at her house. her s*s**r liz and a friend of her s****rs were there with us listening to music and just hanging out. We always made sexual references in most things we did and said. Her and I were getting very turned on touching each other through our clothes we made our way down the hall to there bed room. "F" locked the door and we started kissing, our tongues rolling around in her mouth. She started to take off my shirt then she got in to her bed. They were bunk beds and her bed as on top. I got in the bed with her and we were back to kissing and taking each other's clothes off. We were both naked feeling her soft tits against my body I was so hard she reaches down grabs my cock and strokes it a couple of times then she tells me"I want you in me right now" I roll on to my back to put the condom on. She gets on top of me down on my legs she is stroking my cock while I open it up I get the condom on and she gets right on it sliding it in her taking it slowly until I am all the way in her. She starts riding me my hands on her hips both of us in motion with each other. All of a sudden the bedroom door flys open she falls forward on to me pulling the covers over us her s****r Liz walks in with her friends saying "what are you guys doing" F responds with "none of your business get out" "It's my room I don't have to get out" "Get out on here" "Why what are you doing"F just says it "we're having sex do you mind get out" "No your not" F just sits up the covers sliding off her back her tits fully exposed most of my body exposed "yes we are now get out" Liz's friends gets red and leave the room,  "O my God you guys really are""Yes now do you mind and get out so we can finish" "You guys get out its my room to" There is a moment if no one taking Liz looking at us and F on top of me and both of us looking at her. F says "are you going to get out or are you just going to stand there and look at us" "I am not leaving"I idea of her watching us was a huge turn on for me. I pushed F down on to me a little and slid deeper in to her.  F looked down at me "Who cares" I said. I tried to start going at it again she looked over at Liz and then back at me and then she just went with it and started riding me. Liz was a little more then a year younger but she had sex for the first time when she was *3 she had been with a couple of guys since then. She was a little on the heavy side she was 5'5" brown hair brown eyes and bigger tits then F had, turns out they were 38dd at the time. Liz sits down in a chair across the room as Liz is now riding me and we are back to full motion. I look over and Liz has her pants unbuttoned and her hand down and I can tell she is playing with herself. F sees me look over at her and looks back at me. She moans "you like that" and she leans back grabbing my legs as she rides me thrusting herself harder on to me. She leans back up and grabs my chest digging her nails in to me as she starts to cum. I am going harder and deeper in her she leans down t trying to catch her breath as I keep going getting ready to cum. She bites my neck and says "cum for me" I start cumming and we kiss as I finish.  We look over and Liz is sitting there with her legs open and her hand out of her pants now. "You enjoy the show" F says.  "Very much" she gets up and walks out. F slides off of me and she looks down at the condom and makes a comment on how much cum is in it. She strokes my cock a little before she gets up for us to clean up and get dressed. We get dressed and go back out in the living room and Liz's friends is still brite red "I can't believe you just did" she says to us all. F decided to tell them we have been having sex for a couple of months now.  We continue with our day of just hanging out at her house until there dad gets home and they start to make dinner before I leave.