My step-sister Chi Chi and I were studying anatomy naked and we were curious about a few things when Step-Daddy walked in. As luck would have it Step-Daddy was even willing to help us in the "interest of science". We pulled down his pants and started exploring his penis. It grew harder in our hands as Chi Chi and I took turns exploring it until finally Daddys penis exploded on our hands. Now that our curiosity is satisfied we can get back to studying.