Downfall/Carefully gyrate your pelvis
From Create Your Own Story
Since you came so far, you get adventurous. Kirsten is tolerating your groping, and she hasn't complained about your cock poking her. You don't know much about girl's behavior, but that surely must mean that she is just as aroused as you. That's almost like an invitation to take it to the next level. You move your pelvis until your cock is placed neatly between her cheeks. Then, you slowly start thrusting up and down. Kirsten moans, which is reason enough for you to continue. But as was already mentioned - you don't know much about girls, in particular that girls do not like to get humped by the next guy. Especially not by their brother. What you mistook for a moan of lust actually was a mixture of disbelieve and disgust. As soon as Kirsten overcomes her shock, she starts to scream for help. Bam! Julianne and Debra storm into the room and find you atop of Kirsten with a boner, dry-humping her.
The next weeks fly by like a blur. Your mother called the police, you were arrested for sexual assault. You were released on bail and are now waiting for your trial. Maybe you should have reflected on the deeper meaning of the word 'consent'.