A/N: Prompt from an anon; someone tells Brittany that poly relationships are a thing. Thanks!
"I thought that was cheating." Brittany tilts her head.
Sam and Blaine exchange glances. "Not if everyone involved is on the same page and into it," Blaine says, Sam nodding with his words.
Brittany stares at the two, unblinkingly, her books clasped tightly to her chest. Finally, "Do you want male kisses with Blaine?" she flicks her eyes to Sam.
His lips twitching, Sam tries a wan smile. "It... Might be fun," he admits. Blaine shoots him a disgruntled, 'what the hell?' look, and he shrugs helplessly.
Taking in Blaine's rolling of eyes and her boyfriend's body language, Brittany's eyebrows rise. "Blaine," she turns her attention to the shorter boy, "You're capitol G gay, right?"
It is Blaine's turn to fidget nervously, his hand coming up to rub the back of his neck. "Yes," he answers, "But..." It is Sam's turn to stare at him.
"Hmm." Looking down, Brittany breathes in deeply through her nose. Finally, shrugging herself, she strides forward, leaning in and pushing her lips against Blaine's.
Stiffening, shocked and not really knowing what to do with his hands until Brittany pushes her tongue in between his unresisting lips, Blaine almost instantly wraps his arms around Brittany's waist. "Oh my god," he lets out as they part, staring up at her with a stunned expression on his face.
"And that's not all I'm good at with my tongue," the blonde winks, turning on her heel and slipping her arm into Sam's, "Why didn't you just tell me you wanted to sleep with him?" Barely waiting for Blaine to catch up, taking his place on the other side of Sam, she smiles thoughtfully, "Sex is gonna be hot, huh?"
Looking at each other again before looking away, both flushing, Blaine and Sam clear their throats. "Yeah," Sam manages a faint, shell-shocked smile.
"Hopefully," Blaine finishes. He readjusts his sweater. "Definitely… Definitely a new experience, at least."
Brittany smiles, cuddling into Sam's shoulder. "Awesome."