They got stranded on the island after the yacht party went to shit. Just the two of them at first, Mark and his little sister Lisa, both over eighteen and stuck with nothing but sand, palm trees, and each other. The sun beat down hard, and by the second day the heat made them strip down to nothing. Lisa walked around with her tits out and her shaved pussy on full display. Mark couldn't stop staring at her ass every time she bent over.
"Fuck, Lisa, put something on," he said, but his cock was already half hard in his shorts.
She laughed and spread her legs on the beach towel. "Why? It's just us. You like looking at my pussy, don't you? I see that bulge."
He didn't answer. Instead he dropped his shorts and let his thick cock spring free. Lisa licked her lips and crawled over on all fours. She grabbed his dick and started sucking it right there in the open, slurping loud and messy, spit running down her chin while she took him deep. Mark grabbed her hair and fucked her face, pushing until her nose hit his stomach.
"Goddamn, sis, your mouth feels like a fucking cunt," he growled.
She pulled off and turned around, presenting her ass. "Then fuck it. Fuck your sister's pussy."
Mark slammed into her from behind, driving his cock balls-deep into her wet hole. Lisa moaned and pushed back, taking every inch while he pounded her on the sand. Her tits swung and her juices coated his shaft. They fucked hard and fast, no romance, just raw need. He slapped her ass red and called her a dirty incest slut while she came, clenching around him.
They didn't stop after that first fuck. Every day turned into nonstop sex. Mark ate her pussy for breakfast, tongue-fucking her hole until she squirted on his face. Lisa rode his cock in the shallow water, bouncing and grinding while waves splashed around them. She begged for it rough: "Choke me while you fuck me, brother. Use my cunt."
By the end of the week the rest of the family showed up looking for them. Their older brother Jake and cousin Rachel, both adults, found them naked and fucking under a tree. Instead of shock, everyone joined in. Jake bent Lisa over and shoved his cock in her ass while Mark fucked her pussy, double-stuffing their sister. Rachel sucked Jake's balls and licked Lisa's clit at the same time.
The island became one big fuck zone. They took turns, switching partners, filling every hole. Mark came in Lisa's pussy while Jake unloaded down her throat.
Rachel rode Mark's face and squirted while getting fucked from behind. No one held back. They fucked in the sand, against trees, in the lagoon, calling each other filthy names and coming over and over until they were all sticky and exhausted.
When rescue finally came, they didn't want to leave. The four of them kept the incest going in secret back home, but nothing beat that raw island sex where they could fuck openly whenever they wanted. Lisa still texts Mark sometimes: "Remember when you fucked my ass on the beach? Come over and do it again."
