Wee boy walks past his mum and dad's room, and hears a commotion and opens the door, and sees his dad giving his mum a good seeing to. The wee lad walks off in disgust, and the next day his gran visits. The dad hears a noise from the sons room, and opens the door to be confronted with the boy shagging his gran. "WTF are you doing??!!" Asks the dad, to which the boy replies "it's not so funny when its your mum is it?"