one day kid 16 yrs or so comes home to find his step-dad screwing his mom, the dad looks over his shoulder n winks at he kid and keeps going at it. the kid goes up to his room traumatised at what he just saw but after a few hours decides something must be done. so a few hours later dad walks up the stairs opens the kids door and see's the kid banging grandma, kid looks at the dad, winks and says "haaa aint so funny when its ur mum is it."