None of the three could say how exactly it had happened. It hadn't started with a question, nor with too much drink and too little inhibition. But King Arthur had two bedmates. He had two, warm, blanket-stealing, overaffectionate bedmates.
But it was alright, because no matter how many times Gwaine threatened to toss the other two from Arthur's large, lavish bed, or how much Merlin complained that his toes were too cold... they always stuck Arthur between the two of them, nosing into his hair (Merlin's favourite activity next to sucking Arthur's cock between his bruised red lips) or brushing long fingers absent-mindedly over his stomach (Gwaine's favourite activity next to fucking Arthur's arse) as they burrowed under the covers.
Tonight was no different for them, save for the frigid draft leaking in from the windows. The days were edging nearer and nearer to the solstice, which meant more time pressed tightly between two of Arthur's favourite people but also the need for more warmth.
"If my bum is frozen in the morning, I demand my own manservant," Merlin said, curling against Arthur and nipping softly at his earlobe.
Arthur arched into the attention, while Gwaine muttered to his left, "If your bum has frozen in the morning I'll fuck it back to health."
"Such a way with words," Arthur whispered in response, turning to Merlin and kissing his petulant expression away.
"Sire, what would you have me do?" Gwaine asked, tone serious as he watched Arthur and Merlin lap at one another's mouths. Arthur liked this best, when Gwaine forgot to keep others at a distance with his quick banter and instead pulled them close to his heart. Times like this made Arthur realize how large the place in his heart was, the place reserved for Gwaine.
"Kiss him," Arthur said against Merlin's lips.
Merlin reached over Arthur and grasped at Gwaine's hip, pulling him flush against Arthur's back under the furs. They kissed above Arthur, tongues tangling, but Arthur never once felt ignored.
Gwaine's hand slipped beneath Arthur's britches, palming his growing erection as Merlin's hips pressed in just a layer away, seeking friction.
"Gods—" Arthur choked out when Merlin finally pushed his britches down, waiting in anticipation. Soon they were all three naked and writhing and it was perfect.
"Arthur," Merlin mumbled, grabbing at his hair as Gwaine again took hold of his cock and slicked it down with his precome. "Let me fuck you."
Arthur groaned and squeezed Gwaine's fingers around his own cock to tamp down the sudden rush he got from Merlin's words. The feeling was just as unbearable in his chest, like his heart needed still more room for Merlin, just next to Gwaine.
"Yes! Gwaine, I need—"
Gwaine kissed Arthur as Merlin retrieved the oils and warmed them against his shaking hands. His fingers were clumsy, but only with lust. If anyone knew how to take Arthur apart it was Merlin.
Merlin kept up a monologue as steady as his thrusts, whispering love-filthy words in Arthur's ear as Gwaine slotted his own eager cock just next to Arthur's, thigh hitched over the others' joined bodies and hands caressing restlessly.
"Warm," Gwaine murmured. Where Merlin was loquacious Gwaine was virtually silent with need once things got started, actions speaking for him. Arthur was sure that he listened just as intently to Merlin, as well.
"Gods, you should feel—oh, Arthur, I love fucking you… You're so tight and warm and oh, I'd live inside you if I could—"
Gwaine laughed lightly, appreciative, as Arthur leaned back on Merlin's shoulder. Grabbing Merlin's arse and making him stay deep, just for a little while, Arthur came all over the planes of Gwaine's twitching belly.
Merlin fucked Arthur's squeezing hole until he came as well, one hand clenched in blond hair as the other clenched Gwaine's tanned hand. Gwaine followed swiftly with a grunt and pulsing, wet heat against Arthur's thigh.
After, sated and gasping hurt little breaths as they clung together, Arthur pulled his bedmates to him and pressed sleepy kisses to their brows.
"Complaining now, Merlin?" Gwaine asked after a moment.
Merlin mewled with satisfaction before uttering a slurred, "Love."
Arthur fell asleep, sticky but blissfully content.