Her sister.

As Jessica skipped upstairs, her sister, Brook, hurried after her. You wait a minute, then follow. You go to the bathroom door, listening. The shower is going, Jess is in, Brook sounds like she's at the sink. She's asking Jessica if everything is alright. You quickly open and close the door. Brook is staring at you in surprise. You turn her away from you.

"Brook, right? Pull down your jeans. Now." She looks thoroughly confused, but does it. You pull her tank top down, too. You grab her hips and pull them back, making her prop her butt up some as well as stick it out. You push your cock into her wet slit and start humping her hard. "Worried about your little sister? That's so sweet.... here, I'll let you know how she felt...!" You lean in, fucking her harder now.

"Uh...Uuuh...! Oh.... Oh my gosh...! Uuh...Uh! Uuh..! It's... so good... unh... unh..! Unh...!" Brook looks over her shoulder in disbelief. She started pushing her ass out more without realizing it, waves of pleasures rolling over her. "I... I want it so bad... but I shouldn't.... Unh! Uunh... Uunh.... Mmm- mm! Aah..! Yeah...! Yeah.... Mm..! Aahh... Ahh...!"

Jessica peaks her head out of the shower. "Are you both in here? Geez... is a little privacy too much?" She asks sarcastically. She closes the shower curtain again. You lean into Brook's ear.

"You want to keep your sister sweet and innocent, I get it. But.... I really like doing dirty stuff with your cute little sister...! She loves it they way you're loving it right now.... know what else I can make her like?" You go to the shower, stepping inside. Brook scoots over peaking inside.

Jessica giggles as you grab her waist. You turn her towards the wall, press her up against it. You start shoving your cock into her tiny, young butt. "Jessica... I think you have the cutest little ass.... this soapy water is letting me get into that tight, perfectly round behind..." She gasps, eyes wild in uncertainty mixed with excitement.

"Aaa-aahhh...aaahh...! Ah.. Ah... mm-mm..! Uunh...Unh! M-My.... my ass...?! Uu-unh...unh..!" You spin her around to face her sister, but keep fucking her. "He... He's using my butt...Mm! Uhh! Uuh! Uuh... uuh... why are you watching? You like watching your little sister's innocent little asshole get stuffed with cock.... fucked so good I don't want to stop him.... uuh! Uh...uuh...uuh.... yeah.... uuh... uh huh.... fuck my cute little butt.... Ah! Aa-aahh....Aah...! He.... He's cumming.... Aahhh!"

Brook has her hand between her legs, biting her lip. Jessica looks pleased with herself in a devilish way.