Well, i got a named sister, we do not share blood, but still treat each other as family members. So/ one day, we had a samll party, i tryed to have some romantic with friend of her i didn't get any feedback, but sister invited me to sleep with her. Both of us had a hangover in the morning, all guests went home at night and we were alone in the flat. I tried to make some fun and tried tickle her. She laughed for a minute and than her knee with all her mifht got in my balls, i was very shocked, but thought that it was an accident, so despite the pain continued. "didnt you get me clear?" with theese words another knee hit me. I let her go, but she was already in anger, grabbed my balls and said"It's time for me to get some fun" She squeezed my balls very hard, I screamed but her grab was tight. 3 minutes became eternity, untill my cock rised"Oh, you like it, right?" My balls became her toys, her stressballs in 20 minutes i came and started crying, fell on the floor with sore balls. And in a second recived kick to the balls, she had no mercy. She turned me on my back, got my cock inside, grabbed my balls and squeezed so and tight i thought she will rip them off. She was so wet and sadistick, i dont know how much time was it, but my balls were hardly alive, after all she gave me a blowjob and said"it was fun, we should do it again", i will sure have no kids, after that it was painful to walk for three days, but do u know what? We now do it regulary