okay so my first answer was a little salty (not at anon, just at jkr), but like. okay so they. like, they’re the other halves of one another. they’re two pillars leaning on one another, in support and solidarity. remus thinks that Sirius is so bright he’s blinding, that he shouldn’t even be allowed to look at him. he’s a rare thing, a beating heart, and remus is so, so afraid of breaking him.
Sirius sees remus as like, something combustible or explosive. when it’s just sitting there on its own, all innocent like, it can’t really do any harm—but when you add the right elements or drop a matchstick close enough, the whole place goes up in smoke. remus is TNT and dynamite and exciting and fascinating and dangerous, really, when one thinks about it. the sweaters and the mismatched socks and the soft tufts of brown hair falling into his eyes hide it well, but no matter what he’s still got claws, still got teeth built to bite.
They love each other. they hate each other. they think the other is the funniest fucking person to walk the planet. remus would die for Sirius, really. would endure a thousand transformations all at once just to save him. Sirius, in turn, would take the curse on for remus. he’d eat the whole damn moon if he could, actually, just to make the pain stop.