rabbot teaching their twins mel and dennis how to fuck each other? while they fuck them?? robby holding dennis's hips while mel lays back on top of jack, who's been playing with her nipples and fingering her open to get her nice and wet for her little brother. Mel and Dennis are so nervous but they love their dads and each other so much and they both want to feel good. Robby and Jack cockwarming in their kids' asses while they guide their twins to fuck each other. Mel feeling so overwhelmingly full and loved with her brother's cock inside her and her dad's cock in her ass and her daddy's tongue in her mouth. She has 3 pairs of hands and lips all exploring her body and it's enough to make her overactive brain finally switch off.

dennis meanwhile has a hand on his sister's stomach (where he can feel his cock sliding in and out of her) and the other hand behind him on his daddy's thigh and he thrusts himself between his sister's heat and his daddy's cock. his dad pulls him down to kiss him over his sister's shoulder and he's suddenly pinned between his dads with his sister's breasts pressed against his chest. He can feel his cock both inside his sister and against his own stomach as he ruts into her and moans into his dad's mouth. His dads' and sister's hands all knead and grab at his body, encouraging and loving him — which only makes Dennis rut harder.

"Yeah, Denny?" their dad pants against his lips. "You trying to get your sister pregnant or something? Trying to make me a grandpa?"

Dennis isn't sure if he's serious, but he groans at the thought, nodding frantically and thrusting harder.

His daddy grabs his hips from behind, slowing him. "Ah-ah. Ask your sister first."

Dennis groans and twists away from his dad's lips. He pants between frantic kisses on his sister's neck. "Can I, Mellie?"

His dad smacks his hip. "Can you what?"

Dennis jolts and tries again. "C-Can I get you pregnant?"

Dennis hisses when her blunted nails suddenly dig into his ass, urging him deeper. He feels her nod against him, but her voice is muffled by their daddy's mouth.

"Mike, c'mon," their dad scolds. "Let him hear her."

Their daddy's frustrated groan ripples against Dennis's back and then his mouth is on Dennis's neck, sucking and biting petulantly.

When his sister doesn't immediately answer, Dennis hears a slap near her thigh. Then a breathless, disoriented voice by his ear.

"Yes! Yep! Sorry, I- just-" Dennis feels her swallow down a moan. "Keep- keep going. Until you-" Another swallow and a nod.

Dennis nods into her neck and mouths openly against her skin. His breath hitches when his dad's fingers dig into his ass, clenching around his sister's hands, and pushes hard, rutting his son into his daughter at a brutal pace.

His dad's eyes have a mischievous glint when they catch his over his sister's shoulder. "Wanna race, kiddo?"

Dennis feels his dad's cock start to move inside his sister, pushing up against the already tight space he's occupying. Dennis bites his lip and nods, then surges down to capture his dad's lips again.

---

Jack groans into his son's mouth as his cock swells inside his little girl's ass. He reaches up to grip the nape of his son's neck, hand flexing as he holds Dennis's lips to his. Between open mouthed kisses, he can see Mike start moving above them. His brow is creased with concentration as he thrusts deep inside their boy from behind and ravishes their little girl's lips, neck, and jaw. His eyes, when he opens them, are shining — dark with need yet glistening with awe-filled tears as he stares into their daughter's impassioned face.

Jack thinks he's never looked so gorgeous in all their life.

Dennis's teeth tugging at his lip brings him back to the task at hand. Jack tightens his grip around his daughter's hips and pummels up into her, maybe a bit rougher than he should. But his little girl takes it like a champ, even reaching down to thread her fingers through his bruising grip on her hip. 

Jack pulls off of his son's mouth to suckle at his daughter's earlobe. "That's it. That's my good girl," he whispers as he reaches around to tease at her nipples. "Your brother's cock feel good, Mellie bean?"

Mel nods and leans back into her dad, chasing his voice and exposing her neck for the taking. Dennis gets there first. 

Jack watches for a moment, letting his son suck a deep bruise into his sister's skin, then he tugs Dennis back by his hair and taps a finger over his daughter's lips.

"Go on, Den," he prompts, "Kiss your sister."

Dennis nods and positions himself over her. He tries to catch her eyes as she writhes beneath him, but she's too far gone now. 

"Hey, Mellie?" Dennis cups her cheek, trying to get her to focus. "Can I kiss you?"

Mel nods feverishly, eyes squeezing tighter and as her chin reaches up towards the sound of his voice.

Jack watches with hungry eyes as his son leans down, tender as anything despite the way his hips crash against her, and parts his lips against his sister's.

Jack's dick jumps in his daughter's ass when his son's tongue flashes between their mouths. He thinks he could watch them like this forever, his kids' faces so soft and pleasured while they explore each other's mouths and bodies. Then his view is suddenly blocked by Mike swooping down to press bruising kisses into his open mouth. 

so in my HCs mel and dennis are usually twins and usually jack is their dad cuz... well. obviously. sometimes i'll add robby as their second dad for extra fun or sometimes becca is their triplet. but i'll try to keep this focused on melden since that's who you asked about <3 <3

usually i hc that mel got jack's tism and den got jack's bisexuality (and curls) but sometimes i'll give mel some bisexual/gay too if it works for the concept. i usually make mel some flavor of ace or at least give her an unconventional relationship with sex and physical touch. sometimes i'll give something like that to dennis too but they'll still have their own specific nuances

so with all that in mind i usually HC mel and den as very very casually physical with each other. i think they kiss each other and snuggle and bathe together and sleep together (nonsexually and sexually) and they just don't see any issue with any of that. they know most people find it weird though so they've learned not to do certain things or talk about certain things in front of others

i think they also both feel very protective of each other and are definitely codependent in ways neither of them feel very motivated to change. they know their twin inside and out (heh) so they're always making sure the other one has eaten/slept/showered etc and even help the other one do it when things are hard. i think at this point they don't know how to fall asleep without their body wrapped around (or sometimes inside of) their twin

i think dennis sometimes feels at a loss because he doesn't have the same neurodivergency as mel does so he mostly just sits and listens and tries to help as much as he can. i also think he lets mel use him as a sensory board, at first because she needs it and then because he likes being touched too. mel's touches are a pretty even mix of sexual and nonsexual, and a pretty even mix of "normal" and strange too. like she plays with his curls or listens to his heartbeat, but she also puts her fingers in his mouth and presses her fingertips to each of his teeth, counting them and naming them out loud as she goes. sometimes dennis pretends to chew on her fingers or bite her when she does this and sometimes this leads to tickle fights or kissing, or sometimes more. especially if dennis decides to suck on her fingers instead

i think dennis likes to touch mel too, but maybe not necessarily in a stim board way like how she uses his body. more in a comfort-seeking way, like how someone would hug a plushie or play with its fur. i think dennis feels most comfortable when he's curled around his twin sister's body while his hands and lips move across her skin. he's not (always) looking to start anything sexual, but sometimes it leads there. it's easy for them to move between sexual and nonsexual acts though since they don't treat sexual acts as a separate from what they usually do. so dennis can play with mel's nipples (thumbing across them or suckling at them) or mel can use dennis's tip or toes or fingers as an oral stim, but they'll also be watching a movie or playing games or study on their phones or laptops instead of having Sex be their main activity

(ok i can't help it i'm bringing in the dads now)

regardless of how mel and den see it and feel about it, watching this happen obviously drives their dad(s) to irrational levels of horniness. when jack sees his twins playing with each other on the couch he'll carefully slip a hand into his shorts and try to keep still and quiet so he doesn't disturb them. jack usually lasts about as long as his son does, but he can't go again right away like den can. i think eventually jack joins in with his twins' snuggling routines and they include him in all the ways they play with and touch each other too. jack usually takes a more active approach with his twins than they do with each other (eating mel out while jerking den, or eating den's ass while he thrusts into mel, etc) but the twins still keep their own interactions and reactions more casual, even when their dad gets really, really into it

robby on the other hand tries to discourage their twins when he sees this happening. he quickly realizes it's a losing battle though. his biggest concern was making sure mel was on the pill, but that was already handled well before he became aware of the situation, so he runs out of excuses quickly. eventually he starts just trying to ignore it. then, he starts watching. then he starts jerking off while he watches. and then finally he lets himself give in and join the fun too

after both dads are involved, the family likes to trade off which twin gets to sit on which dad's lap and warm their cock while they spend family time together. then sometimes dennis will fill up either of his dads while the other fills his sister, or sometimes he'll take care of his sister while his dads fill each other. or sometimes mel will need a lot of sensory input so her twin and her dads will work together to make her feel nice and full