My sister and I were very often alone at home and being older I even became like the man of the house in those circumstances for our family despite my age. My sister is very talkative and when chatting or playing she wanted me to follow her even if she had to go in the bathroom. It is a fact, when alone, she and I had always undressed and stayed naked without any issue or embarrassment when for instance we had to dress or have a shower.  But her fleshy and smooth slit had always attracted and intrigued me so much since I felt the first urge to handle and jerk my pecker. That day I did not think twice and asked her to sit on my laps and ……. before she could choose the most comfortable position my hard cock was already entering her slit.......... Oh my god!   (I can continue and be more detailed if you want)