My father remarried and I suddenly got a new sister. She's beautiful and has a great figure, but she rolls around every day in a tank top and panties... I got an instant erection because it was too stimulating for me at her age... I couldn't resist her jiggling, defenseless peach butt and started pounding her from behind! I knew it was the worst, but it felt so good that I ended up cumming inside her again from behind while she was sleeping! I thought she'd get angry, but... she said, "I'm so horny I can't sleep..." and raped me in the middle of the night! My dried-fish sister's sexual desire was extraordinary!