When I was 15 my mom married my step-dad and he had a beautiful daughter my age. 5'7', 120lb., medium length blonde hair, and sized C tits. We got along very well, but I did not know how well.
One night, it was about 11:30pm, my door opened and it was my sister. She just stood there for a moment, then I realized she was completely naked. She came over to my bed and sat down. She pulled the sheets down and my boxers along with them. Then she grabbed my boner and rubbed me down until I came. Then she took my spot and I fingered her hairless pussy while feeling all over her body and especially her smooth breasts. After she came she left. Almost every Friday night after that we do the same thing, and sometimes more.