"W-what're you doing?" Dean, who has just gotten out of bed, and whose slightly-too-long, unruly hair is sticking up in all directions, almost drops his searing hot cup of coffee as his wide, disbelieving eyes lock on his baby brother.
Sam, who's spread out on the couch right next to the Christmas tree, shrugs- or, it looks like he's shrugging, at least, hard to tell from the position he's in- and scoffs. "Fingering myself." He says it nonchalantly, if not a little breathlessly, and doesn't slow down or show any intent, for that matter, of stopping.
"Why?" is all Dean's half-conscious brain can think to say. He's still standing there, hasn't stepped toward Sam or away from him, and his knuckles are turning white around the handle of his mug.
Sam full-on laughs this time, head falling back, before it turns into a moan and he presses his free hand to his stomach, just above his cock. Which is exposed. Because he's naked. Fully, gloriously naked. "Was just gonna jack off," he explains, voice hitching. "Had some pretty serious morning wood goin' on. But then I started thinkin' 'bout you, an'... I dunno. Needed to."
Finally, Dean remembers that his feet are not, in fact, anchored to the floor, and he half-sprints across the room to his brother, dropping to his knees in front of the couch. "Let me," is all he says.
Sam chuckles, pulling his fingers out and watching as Dean's position themselves at his entrance. "Merry Christmas, big brother."
"Merry Christmas, baby boy," Dean breathes, middle and ring fingers of his right hand pushing inside Sam's already loosened hole, fingers of his right tangling themselves in Sam's mess of chestnut hair. "Merry fuckin' Christmas."