Sirius refuses to consume human blood even if his worst enemy stood before him when he was especially thirsty, he's a "vegetarian" vampire of sorts, only hunting animals so when the craving is extra strong, he eats a lot of pasties
Got bit making out with a stranger the summer he was fifteen. Won't admit it to himself but he was secretly looking for trouble. He didn't even notice the bite at first. He'd had neck kisses before and hickies so he didn't think much of it until he started smelling blood everywhere and picking on heart beats
Refuses to tell Pomfrey, McGonagall or Euphemia Potter. He just doesn't know if he could handle getting the same look they all give Remus. The look of pity for them being monsters
In modern au, ironically calls himself Edward and Remus Jacob (Mary MacDonald and Marlene forced him to watch Twilight)
Uh... Yeah
