This is a true story that happened the summer of 1974.
During the summer my older sister Hilary and I stayed at home while my parents worked. Because we lived in the Texas heat, we would always wear the least amount of clothing possible to stay cool. My sister would always wear tight shorts with a bikini top and T-shirt.
Usually boredom would set in each day after playing board games and looking through my baseball card collection. The boredom would invariably turn to wrestling or other physical games with my sister to burn off energy. I began to notice a pattern develop during these wrestling matches that would find my sister sitting on top of me, holding both my hands down with one hand, and tickling me with the other.
Being a virgin and very naive, it took a while for me to figure out that Hilary was tickling me so I would squirm around while she ground her scantly clad mound against my crotch until she had an orgasm.
After taking half the summer for me to figure out my sister’s motive, I began to help her out by uncontrollably becoming rock hard while she rubbed her pussy against my dick. Needless to say it started becoming easier for her to get me in such a vulnerable position. It became hard to act like I didn’t want this so called torture put upon me.
Once she realized I was becoming aroused as well, she began to let my arms go free and not pin them to the floor. Becoming braver during one of our sessions, I "accidentally" brushed my hand against her tit while pretending to fight her off. Now my sister has very nice tits (I’m guessing close to a D cup at the time) so it was not hard to miss them hanging in front of me. Scared she would say something; I was surprised when she did nothing. So I decided to go further and put both hands on each breast while pretending to push her off. This must have been just what she needed because she pushed back against my hands and ground harder to achieve what I later realized was a strong orgasm.