"I've told you, Alina. I don't share," he says, lips against her ear. Under her skirt, he drags a hand up her thigh, over the curve of her ass—and her breath kicks up, excited, as he grasps the band of her thong, black mesh that she wore because she thought he'd like it, like seeing it on her. "If I'm fucking you, I'm the only one fucking you."
A few inches away, through the door, she can hear the party; clear, the distinct words of conversation.
"Remind me, then," she whispers.
Skimming a finger over her underwear—damp, slick already—Aleksander laughs. It's not a kind sound.
I love jealous, especially if it goes both way, and they actually don't have eyes for anyone else, but they THINK OR FEAR etc. OR if it leads to MMF.