Dawn bit her lip. She hated to admit it, but her brother had become seriously hot. His muscular body, his massive cock - they certainly beat her boyfriend Kevin in every way. And, god, wasn't that just such a sexy thing? To see her little brother outclass grown men, to watch this hunk masturbate like a beast possessed?
She would give anything to watch it a little longer.
Dawn swayed her hips as she approached her brother carefully. She batted her eyelids, playing the innocent, as she cupped Joseph's face with a hand. "Shh, I'm here for you. What do you need?"
Joseph's face scrunched up as he continued to hump the cloth. Surreptitiously, Dawn moved her hips slightly so that it grazed her warm skin as it passed. He let out a moan, then a roar as a sound like stretching rubber echoed around the room, and his body bulked up even more, his height shooting up from 5'8 to a staggering 6'4. His shoulders broadened to make way for boulders of muscle, his neck thickening as his voice box dropped. "Argh, god, make it stop!" he yelled. "It hurts so much!"
Dawn smiled. He'd walked straight into her trap. "Don't worry, little brother. I'll make you feel all better."
She grabbed the discarded ointment and spread it across her hands. Gently, she pried Joseph's thick, meaty fingers, and then the cum-filled towel, off her brother's 10-inch cock. Dawn stared at the throbbing rod with hunger, before sliding her ointment-laced hands across the vein-riddled surface. She'd given plenty of handjobs before, but none to such a glorious cock,
Joseph moaned, his eyes rolling back in his head. The sensations on his dick were alien, but so, so pleasurable. So strong, they drowned out all the discomfort he had felt before, masking the growth that was yet to come. Unconsciously, he bucked his hips further into his sister's hands, allowing her to lubricate every inch of the rod, from the tip where precum flower like a waterfall, down to his heavy, egg-sized balls.
Down below, Dawn had moved on from spreading the ointment endlessly. She started to smatter the thick cock with kisses, working up from the base to the tip, teasing him with a quick suckle as she gently ran her teeth over the hot flesh. But that was just the foreplay. Quickly, she slipped out of her skirt and panties, lining her glistening vagina with his immense cock. She lowered herself down onto it, inch by inch.
The second Joseph felt his cock enter his sister, it was as if a switch had been flipped. He threw his head back and roared, feeling his deep baritone shake the house. His arms snaked around Dawn's waist, he watched as they thickened and bloated with strong muscle, almost in response to his sudden sexual urges. His fingers dug deep into her flesh as his body surged with growth, stopping her from moving as he jammed her body down onto his crotch.
Dawn squealed as the entirety of his cock slide inside her in one fell swoop. The 10-inch cock filled her up so completely, she couldn't stifle the moan of pure bliss as her strong, powerful brother began to move her body up and down, pistoning his dick in and out of her. Against her back, she could feel Joseph growing, his abs becoming solid brickwork, his pecs a concrete shelf. His thighs beneath her own felt like solid tree trunks, and if she looked carefully over his knees, she could see his legs extending as his height increased.
But, even as he lifted her body with ease, and pressed her close to his immense barrel chest, she could feel something happening down below. Each time he slammed her pussy down on his cock, it felt as if extra inches were being added. At first, it had just filled her, but now the monstrous manhood was pressed painfully against her walls, as deep inside her as it possibly could be. Dawn felt herself being lifted. A glance confirmed her worst beliefs; Joseph's cock was now so big, it was growing out of her.
The massive man growled as he ploughed into her stretched pussy again and again, each time fitting less and less of his immense cock within her. His balls, now the size of cantaloupes, slapped against his thigh as he pounded into her brutally. Dawn felt a shiver run through his body, echoing in her own. It was time.
With a roar, Joseph held Dawn firmly against his body as his cock spasmed wildly, coating her insides with his thick, virile seed. He knew she'd be pregnant within the hour. He came at least a dozen more times before finally, he slid his cock out of his sister. The last of the growth came as he straightened, and Dawn numbly rolled over to see what she had created.
There, in their parents' bedroom, stooping so his head wouldn't brush the ceiling, was her little brother Joseph. He blocked an entire wall with his hulking frame, his hands, each big enough to crush a boulder, flexing by his side. His feet looked large enough to flatten his entire body like a pancake. Should he have straightened, she would have fully appreciated his incredible 8 feet of height, but as it was, she could only see his hulking body crunched into a mountain of muscle. But, his face was what really changed. Before, his skin was acne-ridden and childish, with a few wispy hairs the only indication of puberty to be seen. Now, his jaw was sharp enough to cut stone, his eyes wild and dark like a predator who could smell the fear of his next prey. His chin was taken over by a thicket of hair that continued down his chest, over his arms and legs, with even thicker bushes at his armpits and the base of his cock.
And his cock... Dawn wondered how he'd managed to fit any of it inside of her! It hung to his knees at a ridiculous 18 inches flaccid, his heavy, melon-sized balls swinging behind them. They were already full of seed again, raring to go and breed just minutes after his last fuck.
Joseph held a massive hand to his head. "Ugh, Dawn, what just happened?" he rumbled in his new, earth-shaking baritone.
She gave him her best impression of a seductive smile. "I don't know, big boy, you tell me."
"All I can remember is you were helping me with my dick, then you turned around and..." his jaw dropped. "Oh my god, I fucked you, didn't I? Without protection! Fuck, man, what have I done? What have you done to me?"
She did her best to lay an arm comfortingly on his massive bicep, but it was knocked away quickly. "Don't touch me, Dawn!" he growled. He grabbed her by her collar and held her up against the wall. "What the fuck happened? You know something! You did this to me! You made me a fucking freak!"
"So what if I did?" Dawn retorted. "I did what you asked, I made the pain go away and made you feel better. And anyway, were you even happy, being small and weak? I made you strong, Jo, I made you powerful. And, you're really fucking hot, you know that? You could pick up any lady you want, even that Helena chick you always talk about."
He dropped her unceremoniously. "Really?"
"Yes, really!" Dawn laughed. Inside, though, she could feel jealousy start to eat away at her. After the wild ride her brother had given her, she couldn't stand the idea of having her perfect masculine monster go to any other girl. But, she smiled and said, "But, you're not going to be able to get her tired like you are now. Dinner's getting cold, so you should go eat it now, and then jump into bed. Growing boys need their strength, after all!'