``Which do you like better, my sister's breasts or mine?'' My girlfriend's older sister, who generally doesn't wear a bra, has my voluptuous J-cups pressed tightly against my body. I was captivated by the feel of her big beautiful breasts...and as she was invited, I ended up having cheating sex with her. ``If my sister finds out, it'll be over.'' Even though she was right next to me, it felt so good that I couldn't stop shaking my hips and sucking on her huge breasts.