The Mark Of Cain gives Dean some strange desires.

It’s the mark fueling Dean’s wet dreams at night, imagining Sam sinking his teeth into Dean’s flesh, moaning against his tanned skin as blood thicker and sweeter than honey pours into his mouth. It’s the mark wanting Dean to be Sam’s addiction. It’s the mark that wants Sam, needs Sam, craves Sam. It’s the mark that will do everything in its power to keep Sam to itself.

It’s the mark, not Dean.

Yeah, that’s his excuse.

Sam has been Dean’s obsession since as far back as he can remember. And because of that, Dean knows everything there is to know about his little brother. How Sam cries while watching the titanic. How he fidgets with the corners of pages while reading through lore books. How he reads the packaging of gas station foods, wrinkles his face is disgust, and purchases an apple instead.

But Dean’s favorite things about Sammy is the things that Sammy tries to hide. Like how Sam looks up from the book he is reading to study Dean instead. How his eyes dilate and darken with lust as Dean’s lips wrap around the tip of his beer bottle. How his tongue slips out to wet his lips as a stray droplet of alcohol slides down Dean’s chin. And the frantic expression that overtakes Sam’s face when Dean cuts his eyes to the side to look at him without warning. How Sam’s eyes drop back to the book he was supposed to be reading. How a light shade of pink illuminates Sam’s cheeks. How his chest locks up as he holds his breath, waiting for Dean to redirect his attention.

Oh, and the things Sammy does when he thinks Dean can’t hear him. How he moans his big brother’s name in the shower, confident that the running water will drown out his voice. How he muffles a whimper with his pillow while fingering himself at night, trying to keep himself quiet while Dean sleeps in the other bed, unaware that Dean is pacing the strokes of his cock with Sam’s fingers.

Dean can always tell when Sammy is close. His voice gets higher, whinier, and breathless. He starts begging Dean to go faster, harder. That’s when Dean opens his eyes to look at his little brother, knowing that Sam is too lost to notice him. Sam’s writhing in his bed. His slim, yet muscular figure illuminated by the tabletop lamp that Dean insisted stay on.

His reasoning when Sam asked why? Because in case of an emergency, they needed to be able to see, especially if someone or something was to break in. The real reason? Because he enjoyed watching Sam fall apart and couldn’t do that in a pitch black room.

Dean bit back a groan as he watched Sam arch his back; spreading his long legs as his fingers pumped faster and harder. “Fuck~ I’m close~ Please don’t stop~” Sam whined as he pushed back against his fingers.

And as Sam came with his big brother’s name spilling from his parted lips; Dean came with him. Biting into his pillow to muffle a groan that rumbled from his chest; and not because he was imaging Sammy in his arms. Imagining his teeth sinking into that beautiful expanse of skin that was tucked between Sammy’s neck and shoulder. That perfect place where Dean could leave a mark, his mark, on Sam.

His Sammy.