"It's nothing, really. He just... um, well... he... he's being possessive of Remus." When she said it that way, out of context, it sounded admittedly kind of weird. "Um... it's complicated, though. Especially for, er, being nothing."
Right, she was going to have to be very careful to explain this without giving away Remus' secret, which would probably take some time, and that meant getting comfy. She scooted closer, resting her head on his shoulder. "Um... he and Remmy haven't been getting along the last couple days and I was just trying to help and instead Sirius just got all cranky and was kind of a jerk and stuff. He all but told me to back off, as if he has exclusive rights to being Remmy's mate."