It's not his strong suit, to say the least.
Let's keep this to ourselves, you'd both agreed. That was two weeks ago and you've already heard rumours circling amongst your friends about your entanglement with Sirius. It probably didn't help that Lily had caught the pair of you sneaking off to the bathroom together at the pub, but you trust her enough to know that she's not the reason behind these whispers.
No, you have no bloody doubt he's gone and opened his big mouth. Or at the very least strongly implied something was going on between the two of you before you were ready to be out with it. It's a delicate matter, though. You're all as thick as thieves—it'd be weird if you came out with your... relationship, or whatever it is, and things turned sour as they often tend to do around him.
No. You want to be sure about the entire thing before the entire wizarding world knows you're seeing the disgraced heir of House Black. Surprisingly, he hasn't said anything totally incriminating yet. Well, until you're all gathered at the Potters to watch the Quidditch game on their telly.
He doesn't meant to let it slip. He really doesn't.
Sure, he has a big mouth. But he's used to keeping this particular secret. All for the sake of not scaring you away, of course. That was the last thing he wanted, no matter how poorly it went down with your friends. Sirius is just in a state that evening—all because he had been caught by Lily a few days ago. He'd never, ever hear the end of it: he could already tell. And when James and Remus ask what was up, he just... lets it out.
Sitting in the living room as you and Lily chatter in the kitchen, the rest of your friends spread around the armchairs and sofas. Remus is the first one to notice that anything is off.
"You alright?" He prompts, taking in Sirius' hunched, tense figure as he sulks on the other side of the sofa, his eyes constantly trained on the entrance to the kitchen. All he gets in reply is Sirius grunting a vague sound. He's in one of those moods where he's clearly thinking something over hard.
"Something's up," Remus notes, catching James' attention now, too.
The two of them exchange glances, not sure whether to press further. Something was off with Sirius, but neither of them would have expected him to volunteer anything when he's like this. Except after a few beats of silence...
"I'm seeing someone," he bursts out.
Remus chokes on an inhale of breath. Sirius dating? Sirius with an actual person in his life he was having relations with on a regular basis? He couldn't say he'd ever seen that coming. Beside him, James turns to look at him so quickly, he'd almost give himself whiplash.
It doesn't help that at that exact moment you reappear with Lily in the doorway, two bottles of wine in hand and a very bewildered expression. Oh, you're gonna kill him.