My Wifes 13 Year Old Sister .

Most Saturdays we used to go to my girlfriend parents house . They went to the pub mid day . We sat and waited for them . I was sitting on the couch , with my back against the arm . My girlfriend was leaning against me . Wacthing the tv over my shoulder . Her 13 year old sister came down from her room . She was wearing a dress . She climbed on to the other end of the couch . When i say climbed . She did not sit down . She perched on the arm . With her legs spread . She was not wearing any panties . Showing m her pussy . She stayed like that for ages . I was looking at her pussy . She was giving me a strange look . That said , you like it . I got an erection . Hoping my girlfriend would not feel it . I desperately wanted to touch her pussy . When my girlfriend moved . Her sister dropped on to the couch , sitting as if nothing had happened . After this , a few times . Her sister would how me her panties , sometimes pulling them to the side . To show her pussy . If my gilfriend had gone to the shop . Her sister would get really close to me , showing me her panties , or pussy . Somtimes bending over in front of me . It was hard not to touch her . I was scared what she would do if i did . My girlfriend never knew .