So one day little Billy comes home and hears a loud bumping noiseand yelling coming from upstairs. He goes upstairs to investigatesand opens the door to his parents bed room.

He sees his father having sex with his mom,and he's really givin it to her. his dad looks over, smiles and gives a little laugh then nodes his head for Billy to leave so they can continue busuiness.

After mom and dad finish he goes downstairs and is appaled to see Billy with grandmom bent over the couch, giving it too her really, really hard.
'
Dad screams, "What are you doing?!"

Billy just smiles and says, "Its not that funny when its your mom is it?"