Incest Seduction/Wait for a minute to try to keep it from slipping
"You're totally going to lose. Has it even been 5 minutes? Maybe you should try squats instead of yoga!"
With your brother's stream of encouraging words, you take a deep breath to think about your options. It would take nothing to just grab this thing and move it back into place but that's at least against the spirit of the bet. Maybe you can back up against a chair? Or maybe... if gravity pulled it out, then gravity can put it back.
You turn back around so you can set your stack of dishes onto the table. Then you place your hands on the table's edge and take a careful step backward before leaning forward. Slowly, you dip your torso towards the table while rising onto your tiptoes and maneuvering your butt into the air. You peer over your shoulder anxiously. It all has to be one smooth coordinated movement to not let go of the handle prematurely while doing your best to angle the head of the spatula toward your body.
You're just getting to a point where you feel confident about your positioning when the spatula shifts again. This time it shifts in your favor, sliding a little deeper into your crack. Excited by this, you gradually rotate your heels outward to help open up your cheeks. The spatula then slips in but also slips down. You drop your heels and clench your butt as quickly as you can and end up grabbing part of the head along with the shaft but it's nestled securely into the crack of your ass once more.
It's only after you retrieve the dishes from the table and are on your way back that you realize your brother's taunting has stopped. It was right when you pushed your ass out towards him. Bending over and opening your legs must have been distracting enough to get him to shut up. You weren't trying to give him a show... but you hope he liked it all the same.
You walk back proudly and stoically - as much as you can with a utensil lodged in your butt - and try to let your physical prowess speak for itself. Zack does try to rib you some more but you merely grin. Once you're stationed in front of the sink you're basically home free. Dunking and wiping and setting things aside, you peel through the dishes like flipping through a magazine, paying virtually no attention to anything, just aiming to get to the end. It's probably the sloppiest attempt ever at washing anything but you're way more concerned with winning the bet than you are impressing anyone.
Fearing his impending loss, Zack decides to play dirty. His fingers jab into your side then flit up over your ribs and into your armpit to tickle your exceptionally vulnerable body. You nearly throw a dish at him in response.
"Stop! AHHHahaha! Cheater! Cheater!" you shout.
He doesn't of course. He gropes your figure and attacks your weak spots, which he knows well, forcing you to either defend yourself or let him accost you. The one positive is that being tickled makes you clench your bum harder but it sure doesn't help you get through the dishes faster. Since you're so close to winning you refuse to let him distract you. With a tenacity befitting your family you bite your lip and let him molest your naked body in order to finish the last few items in the sink. You can tell he wants to do something even worse than tickle you, but he holds back.
Your brother finally stops once you pull the spatula from your butt and spike it into the sink to signal your victory. "HA! I did it! I told you I would win! Even though you're a cheater!"
"Whatever. We never said I couldn't touch you. Only the spatula was off limits."
You poke Zack in the stomach. "I'm pretty sure a girl's body is supposed to be off limits to boys, period. Especially when she's naked, let alone your sister."
He pokes you back, right in the middle of your left boob. With a shocked smile you slap his hand away as he replies, "I'll touch you wherever I have to in order to win a bet."
"Yeah, well... nice try but it didn't work! Oh, and I guess you ARE a perv! Well pay up mister pervert!" You pull up on the bottom edge of his shirt, perhaps overzealously. He struggles against you for a moment before wrestling his shirt out of your hands.
"Says the girl trying to strip her brother. Just give me a sec." Zack starts to lift his shirt himself then pauses. He looks nervous, as if someone else is watching. But after he riled you up to such an extent you're not nearly as patient or cautious as he wants you to be.
"Are you even gonna do it?" You place your hands on your hips and glare at him saucily.
"Just... this is weird, alright? What will we say if mom sees us? Or dad?"
"Your problem." He just scowls at your attitude, which induces a groan from you. "I dunno! Say I convinced you to try nudism, since mom thinks that's sooo great. Or that you didn't want me to feel alone. Or you wanted to shame me back into my clothes. I don't really care because I won the bet. Now strip!"
Zack evades your grabby hands once more. "Okay! I'll do it. Settle little rabbit."
He peels his shirt upwards but you're way too antsy to actually leave him alone, especially after he practically tortured you while trapped at the sink. Just as his arms lift into the air you shoot down and grab either side of his sweatpants. With a firm tug you pull it off of his waist and push his bottoms down his legs in one motion. But leaning in so close to your brother turns out to be more dangerous than you thought when he smacks you right upside your head. You pull back as soon as you're struck but lose your footing when you realize what hit you: Zack's stiff cock.
A dull thud is heard when your butt lands straight down against the tile. You're gobsmacked by what just happened. More accurately, your gob was smacked, and by the longest, thickest cock you've ever seen in real life. It's also true that you've never actually seen one before now, despite daddy sneakily stealing your virginity away from you while making breakfast. You never even got to hold daddy's in your hand before he slipped it inside you. So even though you have no way of comparing them like this, your brother looks at least as impressive as daddy felt.
"Fuckin hell sis! Did you really just dick-whip yourself in the face? That's... actually, that's pretty funny!" Zack laughs at you and tosses his shirt onto the counter.
"Well I... How was I supposed to know it would do that?" you ask, staring at him while you stand. "You're not supposed to get a stiffy from your sister you know!"
Stepping out of his pants, he stutters a little before responding, clearly a little guilty about being hard right now, let alone naked. "Yeah, well I guess it's a morning of firsts. But you're hardly one to talk."
"W-what do you mean?" Does he know daddy fucked you? You're not totally sure what to think of that yet yourself, so you didn't really want your brother to judge you over that.
"C'mon. You're clearly enjoying running around all naked. We can all tell."
"Oh. I mean, no! Listen, I'm telling you, it's just a bet. Maybe you want me to be all 'excited' or something, but I don't even-"
You're stopped short when Zack begins speedily flicking one of your pointy nipples with the tip of a finger. With an audible gasp you throw your hands up over your boobs to protect yourself.
"Zack!"
"Yep, they're about the same."
"Same as what?!"
"As when I nurpled you earlier." He reaches down to collect his pants from the floor. "I don't know why you won't just admit it. I bet you've been horny all morning. My dick is at least honest about it."
The contrarian in you wants him to be wrong. You've been just as embarrassed as you have been anything else so far today so it's totally unfair for him to label you like that. Cold nipples get hard too! If only you weren't so warm. But even if he was wrong, you have been flush with both embarrassment and excitement for so long now that you're starting to get mixed up between the two. He just has no right calling you out on being turned on with his huge thing bobbing out in the air in front of him!