I still find it interesting how so much of the perception of Sirius as a character is swayed by his haughty expression.
Most metas (this is not a dog against those btw, I love Sirius metas, just want to add my own) etc I've seen go with this, his ultra love for james, and his derision towards Peter as the most prominent shows of his character, and infer meaning into every other relationship he has from that point out.
And I think these are outliers.
He looks haughty? Some people are born with resting bitch face, what of it?
And I'll discard any mention of James and Harry right now, bc these are outliers of the greatest magnitude, and looking at every relationship Sirius as extensions of his love for james imo just cheapens his bond to him.
His derision towards Peter is very reasonable, and also the most obvious outlier, and I don't think I need to explain it further. Instead I'll add snape and mundungus fletcher into the mix here, and go on to talk about the often-talked-about usage of certain descriptors within the black family towards people they don't like. As others have pointed out before me, the preferred way to insult people within this family is to insinuate uncleanliness. Walburgas portrait, kreacher and I think also Phineas nigellus use these kinds of insults on a pretty regular basis - many of which go against Sirius as well. And Sirius has adopted these insults, and uses them when he really wants to cut deep. He has many people to be angry with, is surrounded by a whole lot of poor people (for example the entire weasley clan, Remus, and mundungus fletcher), and we even see him in battle.
But he notably uses these cleanliness based insults on two specific people: Peter, and snape. What do these two men have in common? For one, obviously, they all went to hogwarts at the same time. For another, Sirius has, or had had obvious respect for both. Peter as one of his closest friends, as a person he confided in and cared for, and who he then expected to care for him in return (and we know how that turned out). And snape as a rival. As much as Sirius likes to insult snape to his face, he also never misses an opportunity to praise his intellect. Similarly to the way he praises and goads bella in his last duel.
Meanwhile, again, he purposefully surrounds himself with people, who the malfoys regularly call dirty ( the weasleys, hagrid, Remus, hermione), and is also on notably good terms with mundungus fletcher, who everyone from the order likes to call these things too. All of which Harry has described in several shades of dirt as well, tbh. And I'm saying this not in a 'oh wow, the rich boy lowers himself to the commoners' kind of way, bc to me he never gives anything close to this impression. The weasleys come closer to this kind of mindset toward any kind of marginalized person lbr.
What we do see, though, is sirius being incredibly forthcoming and caring towards literally everyone.
He has discussions with hermione about elf rights and their projections of the coming year. He obviously cares about Ron's well-being, long after he mauled him. He jokes around with the twins, and helps them with their inventions. He forgives Remus for thinking Sirius was the spy. He makes a considerable effort to be friendly with Molly after their fight. He adheres to dumbledores bs orders. (I think he told ginny about the repellant charm on the doors but don't quote me on that.) He had the most emotionally honest relationship with lily we see in the text. He cared so much about Peter that lily notified him of his emotional state as something Sirius should see to. He organizes the best Christmas he can manage to keep everyone's mind off of their worry for Arthur. He came close enough to kingsley for inside jokes to develop - jokes urgent enough to be passed to him as quickly as possible.
In my eyes Sirius Black is singular in the way he develops relationships, and in the way he cares for everyone he surrounds himself with.
Even with those he hates.
