When people look at the sixteen year old Sirius Black, all they see is beauty.
James sees his elegant, shining hair, falling across his face and ending just below his ears. It was cut by Sirius after his mother ripped a chunk out; the messy bangs and uneven fringe fall over his eyes, but he refuses to let anyone cut it because he's got a thing about letting people near him with sharp objects (he's really afraid, but of course only James, Remus and Peter know that, because he doesn't tell anyone else). It shines endlessly in the light, and when he bleached it for a dare in the holidays, and he was suddenly bleach blonde, it just looked better- if James did that, he'd look like a twit, but Sirius can pull anything off because... well, because he's Sirius.
When Remus looks at him, he sees the flawless skin, so unlike his own ragged one. He sees how the creamy, smooth flesh turns beautifully tanned the minute the sun touches it. He envies how there was only one spot, ever, on that unmarked face- but how even when it was there, Sirius brushed it off, because to be honest he really doesn't give a flying monkey's. Remus notices how whenever Sirius gets embarrassed (when Remus found out he wrote poems) or ashamed (when his mother started screaming at him in front of the whole school) or over excited (when James' mum sent him a Christmas present- his first one that wasn't passed down from his descendants) or angry (when Malfoy hexed his little brother) but he's trying not to show it, those smooth cheeks will turn a dark shade of red, and he'll try to hide it but it's so obvious.
Peter notices how elegant he is; how, even though he's small and slight for his age, legs are so damn long. So long, in fact, that even Dumbeldore joked about presenting him with the Legs of the Year award, given to the longest legs on a teenage boy- and, while Sirius goes through a clumsy stage because his limbs are growing faster than the rest of him and he can't keep up, he's still graceful (even when he falls down the stairs). Peter sees how precise every movement is; the flick of his head to get the damn fringe out of his eyes; the sweep of his arms as he indicates his stories; the way he stands on his toes to reach things that everyone else can just pick up (cause even with those legs, he's still as small as Peter.)
Lily stops whenever he laughs, just to listen to the sound. Sirius has a few laughs; one that he uses when he's laughing at something he finds stupid- a snigger, a quiet, degrading bit of noise that he saves for teachers and Snape. The way he laughs when he finds something genuinely funny- his face cracks in to a huge smile, showing off those little white teeth, and his laugh echoes around, a beautiful noise which everyone likes to listen to, even his enemies. And then, there's the laugh which everyone wants to hear the most. The laugh that he only ever laughs when someone is tickling him. It's strange, but when Lily sits there with her book, watching him squirm, his arms and legs flailing, his eyes squeezed shut, she starts to smile as well. And then he laughs, and it's enchantingly childlike- reminding everyone of maybe a ten year old, innocent and carefree- and everyone joins in because it's bloody contagious. And Sirius'll lay there, in peals of high pitched laughter, subsiding in to little giggles as he recovers from the tickle attack, then he'll open his eyes and look around at everyone smiling fondly back at him, and he'll crease up his eyes and smile back.
Dorea Potter (James' mum) sees his eyes, and wishes they didn't exist, because they're always so full of emotion that only a mother can see that she wants to cry every time she sees them. The first time she saw those stormy grey orbs, it was when he was eleven; James was saying goodbye to his new best friend. Sirius had his back to her. When he saw James smile, he turned and knew who she was immediately. Being a mother, she could read everything, so she saw instantly the transition from curiosity to wariness. She knew then that James had warned him of how the Potters hated the Blacks as much as the Blacks hated the Potters; she knew that Sirius was under the impression that she would strike him maybe, or shout at him, because he was used to such punishments. Dorea just looked back, and trusted her son's judgement; she greeted him, shook his small hand, and the eyes then showed confusion, because this was just another thing that his parents had lied to him about. The second time she saw them they held dread, for Sirius had seen his parents waiting on the other side of the platform, and he'd walked to them, trying to hide his fear but failing miserably, and Dorea had watched him, wanting desperately to bring him back. The third time she saw them they had held happiness, because Sirius had been told he was to stay at the Potter's for a few weeks- more freedom from his family, and time with James. The fourth time was familiarity; by now, Sirius was a second son to Dorea, and he knew she would no sooner hurt him than harm a hair on James' head. The fifth time, they had held grief, for his uncle Alphard- the only other decent Black- had just passed away, leaving Sirius alone.
The sixth time had been unexpected. Dorea had opened the door at one in the morning in the summer holidays, and the first thing that she saw were those grey eyes, filled with tears, despair and pain- more pain than any sixteen year old had ever seen- and, most heartbreaking of all, confusion; for he was just a child, fifteen, deserted and tormented by his family, and now alone, and he didn't know what to do so he just stumbled his way to the Potter's. Dorea hadn't thought, then. She'd picked him up, directly ignoring the flinch that had obviously been picked up from his father striking him; she had carried him through to the living room, and sat him on her lap, and looked in to the beautiful eyes, told him exactly how much she loved him, and held him until he slept. After that, she saw those eyes everyday; those stunning orbs, morphing from pain to delighted happiness under her care.
Sirius didn't see any of this.
When Sirius looked in the mirror, he hated what stared back. He didn't notice the hair, the skin, the limbs, the eyes. He saw his father and his mother, his brother and his cousins. He saw a pathetic excuse for a teenager- ran away from home, from his problems, instead of fighting them. Really, who did that? He saw a boy who deserved to be hated, not loved by James and Remus and Peter and (eventually) Lily and James' mother and father. Maybe that was why he sent Snape to the Whomping Willow that night- maybe he wanted Remus to hate him, so everyone could hate him, so his self hatred could be justified. Maybe that was why he laughed scornfully at Peter every time he shied away from direct attention. Maybe that was why he fought James, insulting his family then punching him. But the thing was, James didn't fight back. He just stood and let Sirius punch him, then he held his fists, and said something ('You didn't mean that, mate, I know you didn't. Why don't you go and lie down now?') and lead Sirius to their dormitory and waited until he fell asleep. Peter didn't snap back when Sirius laughed; he let him, because he knew that Sirius was really making himself feel better, and didn't friends come first? And sure, Remus was upset (scratch that, he was devastated) but he knew exactly why Sirius did it, so when Sirius came up to him, a pathetic, sniffling mess, he forgave him, and hugged him.
Because everyone who knew Sirius knew just he beautiful he was, inside and out, even if he didn't see it himself.