Me and my girlfriend both 18 were telling each other our secrets . It got round to sex , i admitted that when i was young . I had wanked my pal and given him blow jobs , he had done it to me . We had also fucked each other in the butt . My girlfriend had 2 brothers and 1 sister . The house had 3 bedrooms . Her parents slept in one of them . The boys had their own room , and the girls had the other room . They all had large beds . My girlfriend had always slept with her sister who was just over a year younger . From about the age of 5 . She and her sister had started doing things to each other . Kissing , touching , and licking . As they got older she started to enjoy it . Her sister licking her pussy gave her nice feelings . They fingered each other and pushed things in to their pussy . When she was 10 , she had her first real orgasm . Her sister had one at about the same time . Most nights in bed , they gave each other an orgasm . Her favourite was with her sister licking her pussy and finger fucking her . They never did anything with their brothers . This got me excited , i asked her if they still did it . They still livd at home . They had sex the night before . We were in my house my parents were at work . We were laying on my bed . Imagining her doing things with her 17 year old sister . Got me so horny . I got down licked her pussy and finger fucked her . Giving her an orgasm . Then i fucked her . On my own in bed at night , i wanked . Imagining having sex with both of them . It was weeks one day when we were having sex . I told her about my fantasy of having them both on the bed with me . She shocked me , when she told me she would like that . We arranged for them both to come to my house , the next time my parents were at work . That day i had an erection just thinking about it . When they arrived , we sat on the couch talking . They started kissing and putting their hands up each others dress . This was driving me mad . I told them i wanted to go upstairs . We went to my room . They undressed each other , kissing and hugging . I undressed . They lay on the bed and i joined them . My girlfriend asked me if i wanted to lick her sisters pussy . I was licking her and using my fingers . My girlfriend was kneeling next to her sisters head . Kissing her then sucking her boobs . Her sister had her hand beetween my girlfriends legs , rubbing her pussy . Then my girlfriend wanted to lick her sisters pussy . I let her kneel down to do it . Seeing her kneeling , with her pussy exposed . I had to fuck her . Fucking her and knowing she was licking her sisters pussy , soon made me cum . She did not stop licking her sister , until she had an orgasm . Now they changed places , her sister licking her . She had an orgasm . We all lay on the bed talking . They wanted to know the details about me and my pal having sex . When did it stop . I told them about my first time with a girl . When i was 12 . From this day . They always came to my house together . They liked me to watch them having sex . Then i got to fuck them . I fucked both of them . After i had fucked one of them , they worked on each other . This always got me ready to fuck again . Her sister had boyfriends , but she liked to have sex with us . My parents used to go away for months at a time . With my dads work , Canada and North America . When they did , the girls stayed with me . Almos every day , we all haad sex . They were both on the pill . Sometimes one would ride me , and the other would kneel with her pussy near to my face . Letting me lick her . Years later after we got maarried . Her sister still joined us for sex . She got married , but her husband never knew about us .