I was sitting up naked in my bed, still a little shocked by what had just happened. My sister, Marie, was sitting there, also naked. She had just given me my first blow-job and had intimated that she and I were not done just yet. Marie noticed the look on my face and moved closer to me and wrapped her arms around me.nn"Don't worry about anything that happens tonight." She said. "You're my brother, and I would never do anything that I thought would harm you or me in any way. Let's just have some fun with each other, I'll teach you everything you'll need to know."nnI thought about that and realized that she was right. And besides, who better to teach me about sex and girls than my sister, someone who already loves me and who wouldn't ever judge me.nnI nodded my agreement and Marie smiled.nn"Now just lay back, and let's get comfortable."nnWe both lay back on the bed, on our sides facing each other. The rain was still beating on the window outside, and when the flash of lightning would light up the room, I could see her face, her eyes looking deep into my own. We both leaned into each other at the same time, my lips meeting hers as we shared a soft, almost innocent kiss. I was enjoying the delightful wickedness of this all when her mouth open-end and her tongue flicked against my lips, seeking to pry them open. I obliged, and her tongue slipped onto my mouth, seeking mine. As our tongues twirled together, my hands started to explore her body. I reached down to feel her tits, marveling at how soft and silky warm they were. Marries' nipples hardened as I caressed them, rolling them in between my fingers.