When my older sister grew a dick, I wasn't really sure what to say.

Standing in her bedroom doorway after hearing a scream and rushing down the hall, wide eyes fixed on the thick shaft hanging between her legs, I opted for, “Um. Nobody's dying, then?”

Looking up with stunned tears in her eyes, her lower lip wobbled as she tried belatedly to hide it with her hands. “A-Alex,” she stammered, clearly too shell-shocked to yell at me for barging in. “What… what do I do?”

Seeing her so confused and lost triggered my protective instinct, overtaking my initial daze. I had always been the more level-headed and responsible of the two, so despite being a couple of years younger I more often found myself being the one to comfort her than the opposite. Today was no different. Swiftly, I stepped inside, snapping the door shut behind me and locking it.

“Hey,” I said reassuringly, moving to sit next to her on the bed and wrapping an arm around her shoulders. “Hey, it's okay. We'll figure this out. Any idea where this came from?”

“I-I…” she whimpered, her soft body shuddering with nervous sobs as she leaned into me for support. “It was there when I woke up. I'm scared, Alex.”

Biting my lip, I considered my next words carefully. “Let me see,” I said eventually.

“Ew! No, Alex, I-”

“I can't help you if I don't know what we're working with,” I said. “Move your hands.”

Slowly, reluctantly, she drew her trembling hands away, revealing a perfect, pink penis, hooded in soft foreskin and firmly anchored to a hairless crotch. I hadn't seen her like this before - obviously - but I was pretty sure this was new. “Is that… bigger than it was a moment ago?” I asked.

“Huh!?” she squeaked, her voice lifting a couple of octaves as she flinched away. I held her close, though, my large hand still rubbing her upper arm reassuringly.

It was not a good time to notice how big her tits were, straining her too-small pyjama top. “It is,” I forged ahead, reaching down with my free hand to pull hers away as she started to cover her cock again. “Look, you're getting hard. Perv.”

She whimpered wordlessly, half-heartedly struggling to pull away. “Alex,” she warned, her voice far too breathy to be taken seriously. “Now's not the time to be a jackass.”

“On the contrary,” I said, reaching down to wrap my hand around my sister's cock. “As a man, I think I know what you need right now.”

She yelped, but did not resist. Instead, her hips jerked and I felt her dick throb in my palm, growing hotter and harder. “Alex, what the fuuuck…” she groaned, her words slurring as her head fell into the crook of my shoulder, breath hot on my neck.

This was beyond wrong, but her closeness, her softness- and her slowly growing hardness - intoxicated me. “You need to cum, sis,” I proclaimed, with all the authority and expertise of a mediaeval doctor prescribing a round of bloodletting. “Let it out just once, and either it'll go away, or you'll at least feel better.”

“You… asshole,” she huffed, but her cock was throbbing in my hand now, and her pretty face was flushed with red. Apparently without realising it, she was well and truly snuggled into me now, cringing into my embrace as I ran my hand over her perfect shaft.

I marvelled at the way her veins stood out from it, a thick and scrolling texture across the smooth, warm surface. I tightened my grip just enough to be comfortable - per my own solo experiences - and began to stroke it, pumping gently as I rocked her back and forth, whispering soothing words in her ear. “It's okay… I've got you, good girl. You gonna cum for me? You will soon, it's okay… take your time, there's no rush.”

Her breathing became gradually more erratic as her protests died out, transforming into hiccuping, shameful gasps of unfamiliar pleasure. “Aleeeexxxx…!” she hissed plaintively through gritted teeth, her hips jerking instinctively to meet my hand. “Alex, pleeeease!”

Oh, fuck. Hearing my sweet sister beg like that was the final nail in the coffin for my own erection, fighting to escape from my own boxers as I increased the pace of my handjob. Somehow, her shaft was slick and warm, a sticky fluid acting as a lubricant as I felt her tremble.

I knew those signs. The way her breath caught in her throat, the way she lost the ability to say anything coherent, and the needy pulsing in her now rock-hard cock suggested that her lack of experience was taking its toll.

“That's it,” I murmured, my lips brushing her ear. “Let it out, sis. Let me take care of it for you, okay?”

With a plaintive whimper and a helpless stiffening, my sister came like a firehose. “Alex! Alex, I'm scared!” she wailed, forgetting to be quiet as her cock erupted, shooting a torrent of semen in a high arc across the bed.

Swiftly, I clapped my hand over her mouth as I watched in astonishment, eyes glued to her pumping cockhead. My hand quickly became sticky with hot cum as I tried and failed to stem the flow.

The other hand over her mouth didn't seem to calm her down, as her eyes just rolled back into her head as she slumped against me, still pumping out ropes of thick white jizz all over her lap.

This…was going to change our relationship, to say the least.

Hello! Right, well. That was something. I've been avoiding writing or applying to incest prompts for a while, but I think it's time to bring them back.

For charity's sake, here's roughly where I see this scene going:

• You wake up one morning with a dick in addition to your regular genitalia.

• Deliberately or not, you end up showing me and asking for help.

• I ‘help’ by showing you how to jerk off, and our sibling relationship is forever ruined as we start to see each other as man and woman.

• Over time things escalate, culminating in you getting absolutely railed while your cock sprays hot semen all over the both of us.

• Maybe we have a bit of a concurrent plot where we try to figure out how you grew a cock, or maybe eh, fuck it, it's magic and this just happens to people sometimes.

Other things to consider are the sneaking-around aspect - you do not want anyone else, even our parents, to know. Especially the bit about how your brother is helping you discover how great it feels to cum like a man does. I enjoy getting risky and pushing the boundaries of exhibitionism without actually showing anything off.

Other kinks are cum and lots of it, breasts and nipple play, cute nicknames, blushing, squirming and cuddling, teasing and light-hearted bullying, kissing and mouth play, spit, clothing play and more.

RE: your cock, it will not be forgotten. Frotting, mutual masturbation, handjobs, ball sucking, blowjobs, deepthroat etc are all on the table.

Limits are anal (both directions), pain, actual cruelty, toilet and heavy S&M. Full kinklist on my profile.

I left your character relatively blank. I like the idea of a sort of crybaby older sister getting taken care of by a younger brother, but I'm open to you being younger or a twin instead. We should both be in our early 20s-ish, though. Physically I would only ask you to have a realistically sized dick, the rest is up to you. Big chest is a plus, albeit not a requirement..

Think you're up for it? Drop me a PM, as I cannot guarantee that I'll even see chats - Reddit is actively dismantling old.reddit in every way they think we won't notice. I am going to sleep soon, so there's no rush to get in right this second.