The old house creaked under the weight of the storm, but the real thunder was inside. Mark slammed the bedroom door behind him, his eyes locked on his younger sister Lisa, who stood frozen by the bed in nothing but a thin nightshirt. She was eighteen, legal, but that didn't stop the raw hunger twisting in his gut.
"Get on the bed," he growled, voice low and filthy. "Now."
Lisa's eyes widened. "Mark, what the fuck are you doing? Mom and Dad are right downstairs."
He crossed the room in two strides, grabbing her arm and spinning her around. "They won't hear shit over the storm. And you know you've been teasing me for months, walking around half-naked. Time to pay up." His hand yanked the nightshirt up, exposing her ass.
He shoved her face-down onto the mattress, pinning her with his body. "Spread those legs."
She struggled, but he was bigger, stronger. "No—stop, this is wrong!" Her protest came out breathy, edged with something hot and unwilling.
Mark didn't care. He ripped her panties aside, fingers plunging between her thighs to find her wet despite the fight. "Fuck, you're dripping. Forced or not, your cunt wants it." He freed his cock, thick and throbbing, and drove it into her in one hard thrust. Lisa cried out, muffled by the pillow, as he started pounding her deep and relentless.
"Take it, sis," he snarled, hips slamming against her ass. "This is what happens in this family when little sisters get too slutty." He reached around, rubbing her clit roughly while he fucked her harder, forcing her body to respond even as she whimpered protests. Every thrust was dirty, possessive, claiming what blood and proximity made taboo.
Lisa's resistance faltered as pleasure clawed through the violation. She came hard around him, walls clenching, and Mark laughed low. "That's it. Cum on your brother's cock." He didn't stop, flipping her onto her back to watch her face while he railed her again, forcing her legs wide. Sweat-slick skin slapped together in the dark room, the storm outside nothing compared to the wet sounds and grunts inside.
He pulled out only to flip her again, spreading her cheeks and pushing back in, deeper this time, owning every inch. "Gonna fill this family pussy," he promised, voice raw. Lisa moaned despite herself, pushed into another shattering orgasm as he unloaded inside her, hot and thick, marking her.
They collapsed, breathing ragged. Mark didn't pull out right away, keeping her pinned, his seed leaking around his still-hard cock. "This is just the start," he whispered against her ear. "Every night now. You belong to me."
Lisa lay there, body spent and used, the forced heat still pulsing between her legs. Outside, the rain kept falling, but inside the house, the real secret had broken open, raw and inescapable.
