Sibling fucking attraction

How can you keep your dick in your pants when you have a hot sister with big tits coming out of the shower? You want not just a piece of her, but her whole body to be sweaty when jumping on your dick. You never know her abilities of sucking a dick until you actually feel it, and the warmthinside her vagina, untill you stick your dick inside and with smooth and fast moves, touch her G point.