We kissed a lot. My hands roamed all over his shoulders and his back until finally I reached down and grabbed his ass and pulled him harder against me... Mark knew what that meant. He began to move his hips back and forth in a steady rhythm. His cock was wonderful. He would slowly pull back until the rim of the head of his cock would slip almost out of me, and then he'd thrust all of the way into me. It was delicious. It didn't last too long. As I felt Mark's body tense I had to remind him to. It felt a little strange to strip in front of Susan - after all, she was my stepmom - but since she was able to do it so nonchalantly in front of me, I could reciprocate. Before long, the two of us stood naked in our own pile of clothes."Gosh," Susan exclaimed when she saw my ample bosom, "Those are big!"She was exaggerating, but they were definitely bigger than hers. On the other hand, my areola was about half the size of the ones on her, so I guess that made my tits seem a whole lot heavier.. She wasn’t wearing any panties, and I saw her whole pussy. I was instantly so turned on I had to leave. I went to the nearest bathroom and took out my hard cock. I began rubbing it. Suddenly, the door opened and my sister was standing in the doorway, and without thinking I turned and faced her with my cock in hand. She gasped and shut the door. I sat there for a minute too embarrassed to move. But, I knew I couldn’t stay in the bathroom forever so I put my now soft cock away and tried to. We were in her dorm on her single bed and just laying looking at one another kissing every so often till it started getting heated. I was rubbing her back and slowly slid my hand down to her underwear wear and starting rubbing her soft tight ass she then started to bite my lip. I got her on top of me when she took off her shirt and her little nipples were so hard, we continued to make out as i took off my shirt and she kissed my neck. I then got on top of her aggressively and almost ripped.