step-Sister fucks step-dad twice while you (step-Brother) spies through open door. step-Sister notices and closes door. You come into step-sisters room to confront her about her fucking step-dad. She says it was to save the family, you don't care and blackmail step-sister. You say if she doesn't fuck and suck you, you'll tell step-mom she's been fucking step-dad. She reluctantly does what you say, enjoying it so much she calls herself your slut!