Hot Summer Job/You are supposed to be demonstrating for Bree, wait for her to be ready
Forever the chivalrous brother (sort of) you patiently wait and watch as your sister lubes up her dick with Kylie's help. In reality Kylie is doing most of the work. Bree is staring down at Kylie's hands as they run up and down the length of the newly acquired penis. The expression on your sister's face flips between giddy and silly to intense pleasure. Giggles turn into moans which turns into mild hysterics. Between the vibrator and the alcohol that is inside her she's having a hard time doing just about anything.
"Bree? You ready?"
"Lookit! It's... nnnghah... aaaah... izso BIG!"
Larissa giggles again, laughing at your sister.
"Yes. Your dick is huge. Do you want to use it?"
Bree suddenly closes her eyes and holds her breath for a few seconds, all of her focus redirected inwards. You're not even sure if she heard you. Soon her eyes slowly open and she nods in response drawing in ragged breaths.
"Mmmmkay... yea... yea..."
Kylie lies back in preparation, spreading her legs a little wider and poking at her crotch with lubed fingers.
"Okay. All you have to do is take your dick and move it to... are you watching?"
Bree's eyes have already closed again. Her body is rocking slightly, her hands hovering above the dildo pointed away from her. It seems like the powerful little vibe in her strap-on might be more than she can handle.
"Don't move," you tell the still giggling Larissa.
Shuffling behind your sister you grab her wrists and force her to grab onto her dick. Then you inch her knees forward with your hands until you get the dildo butted up to and lined up with Kylie's pink blushing entrance. Although Kylie's cheeks are blushing even harder.
"This is easy Bree. You just need to rock your hips like this..."
You place one hand on the front of her t-shirt and the other on her butt and push in on both at the same time causing your sister's pelvis to roll forward and the dildo to push gently against Kylie's sex.
"...then back. And then forward again. Just keep doing that."
Bree's eyes flutter open then close. But her body does begin to sway forward. Not very much but it's a start.
"That's it. You just have to get it in Kylie. And do it harder."
Your sis gulps air then opens her eyes and mouth with a huge smile.
"Am I having sex?" she asks you pointedly.
"Yeah. You kinda are."
"....ppfffft-hahaHAha-UUuuunnghh..."
Your sister collapses forward onto Kylie who gasps and grabs the sheets frantically. Bree's fall forward managed to thrust the lubricated strap-on up inside of Kylie with every ounce of her body weight. At least three quarters of the thick rod slam up inside Kylie's tight slit before Bree's body comes to an abrupt stop on top of her.
"It's too big! Get off!" cries Kylie, trying to pull away from under her.
"Just wait. It always hurts at first," you assure the scared teen. She's just lucky it was well lubed. You grab her leg to hold her in place and keep her from crawling away. Then you hook your fingers into the tight strap secured to your sister's waist. Pulling back on it you pull Bree off of Kylie a few inches, and the dildo with her. But while that offers Kylie some relief, the added tension and upward pressure of lifting your sis by her strap-on forcesa pitiful and high pitched moan to release from her throat.
A few seconds of stunned silence is broken when all of the girls giggle together at that unexpected outburst. Until you push Bree down into Kylie again. Then only Larissa is giggling, the other two moaning and gasping in unison.
You wager a guess that the strap-on dildo is bolted through the harness to the vibrator poking up into your sister. Any movement or pressure on that big pink dick is transferred straight to the vibe. That might also mean some of those vibrations make their way down the length of that pink shaft as well, ensuring the toy is a truly shared experience.
You help guide Bree in and out of Kylie a few more times before you release her. Under her own power she manages to continue that short thrusting movement on her own, sliding that big silly dick in and out of a half-frightened Kylie. Watching your baby sister Bree fuck this tight little redhead teen with a meaty strap-on makes your balls ache.
"Alrighty Rissa, you're ne-"
You stop yourself, only now noticing that Larissa isn't on the mattress next to the other girls. She's across the room, lip syncing and dancing naked to the music that's still playing in the background.
"Hey, dancing girl. Come lay down," you half-threaten with an absent-minded stroke of your cock.
"No! You have to catch me!" Rissa teases you, slo-mo running around the corner.