I ended up teaching my sister how to swim, because she hates swimming lessons. I couldn't help but get an erection from the swelling of her growing breasts and couldn't teach her properly! Then my sister noticed that I was in a panic because of my erection and asked me to hurry up and teach her properly. I couldn't hold back and asked her to let me do it, but she backed away, saying, "That's a bit much..." I was in despair that this was the end of our relationship, but seeing how disappointed I was, my sister suggested, "Well, if you just rub it..."