Brooke cried out, "Oh fuck, Will, take it easy. Oh shit, that hurts."

I said, "I'm sorry, Brooke," and I paused.

I didn't want to hurt my sister but on the other hand, I had my dick in her butt. Brooke's pussy was tight but her ass was even tighter and it felt like it clench up on my dick. I waited for her to tell me it was okay to keep going and I made sure I went very, very slow. Once, she got used to having my dick up her butt, I ever so slowly pushed into her going fractions of an inch at a time. I would...