I have a nice thick 8 1/2 inch cock with big balls that I was recently working over while thinking of my girlfriend who was giving me nothing but blue balls when my 15 yr old sister walked in on me from school. She stood in front of me stunned not knowing what to do but I was past the point of no return and a few strokes later I felt the warm stream of cum hit my chest and I stroked even quicker to feel another burst of cum hit my stomache. I stroked my cock, my hand full of cum looking at my sister to say sorry but I could not stop. She said she should have left but could not. We both laughed nervously and my sister said no need for her to go to sex ed the next day at school!