Part One -

I follow my step-sister down the hall into our parents room. She has no idea, but I catch her take money out of our Step-Dad's nightstand. After she shoves it in her pocket, I ask how much she got. She turns around so fast and so scared, but still lies through her teeth about taking anything. She's the favorite and our parents want to kick me out, meanwhile, she's stealing from them! Since I caught her on video stealing, I basically own her now. And I use her to my full advantage.

Part Two -

While eavesdropping on my step-sister, I catch her taking nudes of herself with her phone. When she leaves her room to go to the bathroom, I run into her room and steal her phone. As long as I keep catching her in messes like this, I can keep blackmailing her into doing what I want her to do.