Yes/Chad/Calm this down by telling Bree what a pervert is in a way she might accept it
You take a knee and set your hand on your youngest sister's damp shoulder.
"Bree, pervert just means something or someone is different. It would be something that most people don't do. Like drinking pickle juice."
Bree grins knowingly at your comment.
"Most people would just eat the pickles, but you would lick a pickle dry before you ever ate one. That's kinda perverted. We're all perverts in our own way."
"Yeah, but it's not as bad as wanting people to pee on you," adds Emily unhelpfully.
"I don't want people to pee on me!" Bree insists. "Just Chad!"
Emily scrunches up her face. "Why?"
Bree adamantly replies, "Because!"
Your evil side is twitching again. "I don't think it matters whose pee it is, Bree. Would you let Em pee on you if she wanted to?"
"Why would I..." starts Emily.
"Yeah, okay," Bree states, suddenly expanding her pool of allowed pissers.
"Alright. Emily, do you want to pee on Bree?"
She nods emphatically. "Yeah, I do, now that we keep talking about it. Plus... I still have to go."
"Didn't you pee already?" asks Bree.
"I had to stop when I filled my glass," Emily responds with a look of shame, as if she wished her glass was bigger.
You stand up and undo your pants. "Alright Bree, you asked for this."
"Yay! Pee on me!" she squeals, bouncing in place.
"Okay, but only if you sit right there," you order, pointing to the side of the kitchen with the most floor space.
"Sure!"
Your little sis skips forward and plops down onto the hardwood, tucking her feet under her butt and demurely placing her hands on her knees. You take your cock out and watch as Emily turns even deeper shades of red at the sight, even going so far as to shield her eyes from your manhood. Some of her sensibilities still remain it seems.
"Aw, are you embarrassed?"
"Yes, I am! Bree can see my pussy. I can see your... thing. Now I want to pee on my sister. I don't know why I'm doing this!"
That was the wrong question to ask.
"Oh, uh, well, are you enjoying it?"
Emily instantly relaxes a little. "I guess so, yeah. It's just all so dirty."
"Do you get turned on being embarrassed like this."
Emily opens up her body a bit more, biting her lip as she glances down at your mostly hard cock.
"Mm hmm. God... I really am a pervert."
"That's not bad, is it?"
"Yes it is!" Emily throws her hands over her face. "I don't want to be a pervert either!"
You need to be more careful about how you word things.
"Er, but is it okay to be perverted sometimes?"
Em drops her hands from her face. "Yeah, of course it is."
"Then it's not that bad. So what do you say? How about we act like a couple of perverts and pee on our sister?"
Emily excitedly pulls on her shirt and throws you a big smile. "Okay!"
"Finally!" remarks Bree in mock exasperation.
Holding your cock, you step up next to the youngster and strain through your erection. Softening a little allows a powerful stream to burst out just as Emily stands beside you at a different angle. When your strong blast hits Bree in the face she squeaks and shuts her lips and eyes tight. So you shake your dick a little and splash all across her delicate features, the smack of the liquid against her skin the only sound that fills the room.
You watch Emily lift her shirt, tucking it under her chin, and spread her sex just like a few minutes ago before she joins in on the fun and adds her stream to yours.
"Can you open your mouth?"
"Yup!" Bree complies immediately then coughs as two different streams of urine fly past her lips and crash into her tastebuds. You never did say she wanted to drink it.
"Does it taste like pickle juice?" you add.
"Yea-!" she replies while you fill her mouth. Meanwhile Emily is aiming higher, soaking Bree's already damp blonde hair until it is matted to her scalp, the excess running down over her face.
If only mom could see you now, two of her kids pissing on their youngest sister. She would have a heart attack.
After a few more seconds Emily runs dry, leaning forward to squirt her few final pulses over Bree's forehead. Your stream is still pouring into and out of Bree's dainty mouth, but her golden shower is nearly over. You finish up by spraying her arms and chest for good measure, not that her dress hasn't already been soaked by the cascade of piss running down her. A shallow yellow pool has been created by the saturated dress in the small gap between Bree's legs.
After a few shakes you step back to take in the sight of your drenched little sis. She is sitting in a literal puddle that is still being fed by the piss trickling down her face and dripping off of her body. Bree flutters her eyes open and then, before she can speak, swallows a mouthful of your warm "pickle juice".
"This is fun! Can you do it again, Chad?"
"You actually like this?" asks Emily. "I can't believe we're all such perverts..." she trails off, scratching at her slit as her shame and embarrassment rises.
Aaaand your erection is back.
What now?