You go to your Sister and taunt her about the video you have. You decided to use it to your advantage now. She can't believe you caught her kissing another guy, her boyfriend would be devastated. Since she says she will do anything, you want to see her tits. She is reluctant but she exposes her boobs so you keep it a secret. You can tell she is getting really annoyed with you. But it's not enough, you need to see your Sisters pussy and ass. She gives in and spreads herself for you. Now she is fully naked, and you are so horny for your own Sister. You tell her to suck your dick. She doesn't want to, but you remind her about the video. She gets on her knees and obeys her Brother. Your cock is so hard. She starts off slow, super pissed off, then she gets better at it. By the end you fuck your Sisters mouth harder and harder until you pump your load down her throat and make her swallow it. She hated swallowing your load.