Fight dirty while you can!

Robin is still gloating over you while you assess your options. She's got the Rulebook, has an inkling of what it's capable off (and what you've done with it so far), and you can't touch it. And as your sister bounces in place and does the not-touching-you game with the Rulebook in front of your face, your options quickly narrow down. You need to distract Robin, and fighting dirty is the obviously right answer to do that.

"What's the matter, Mikey?" Robin teases and puts her hands on her hips, leaning forward a bit to add to her mocking posture. "Not so fun when you're not in charge?"

"Robin! That's enough!" Heather scolds, gathering her wits and trying to reassert herself as the mother in the room, which gets a reflexive cringe of guilt from you. "Your brother is stressed enough as it is--he's so lonely right now, after all. And being bullied by his big sister isn't going to help!"

"But mom, don't you see what he's--" Robin starts to explain, only to be interrupted by you as you tackle into her. She stumbles back against the bedroom door, slamming it shut as she oofs loudly. "Michael, what're you?!" she starts to exclaim, but her words are cut-off by a yelp.

Your hands move over the thin stretch of fabric over your sister's tits. She's squirming and trying to pull back from your hands as you fondle her modest B-cups. It's kind of crazy to realize your sister got none of your mom's voluptuous genes, but it never stopped you from checking her out before. Or from appreciating the feeling of her hard nipples poking through the bikini's thin fabric. You give her a squeeze and pin her to the door by leaning into her. She sighs and shimmies helplessly, blushing, and drops the Rulebook to the floor with a sigh.

"Alright, now you two have both had some good hits." Heather says, stepping behind you two and strategically ignoring the sexual nature of the situation. "Now make up and finish getting ready, your father--"

"What daddy doesn't know won't hurt him," Robin says with a knee-jerk reaction, her deep brown eyes widening a bit as she understands why she's saying that. She glowers at you. "You little p--"

"Shut up, you love it," you growl back at Robin, pressing your lips against hers. Her eyes go wide and she grunts against you, trying to push you back. Instead of giving ground, however, your hands slide her bikini straps off her shoulders. The small cups of fabric over her tits linger for only a moment, then fall away to reveal her perky little breasts.

"Oh god, Michael!" Robin protests, trying to flatten herself back against the door and slide to one side to slip past you. Your hips move forward and pin her in place, your crazy porn-cock rubbing against her hip as you do so.

"Young man, do we really have time for this?" Heather says, putting a hand on your shoulder and leaning in so close her words are in your ear, making your spine tingle. You're not sure she's trying to give you ideas, but that is what's happening.