Curate, connect, and discover
When Harry is born, Sirius is dead terrified of holding him. He will do literally anything to avoid it. He spills hot coffee on his arm when Lily offers the first time, playing it off as an accident. He lies that he hurt his elbow in a battle when James tries to hand Harry over. He casts a wordless, wandless spell on his arm to cover it in rashes, saying he shouldn’t, just in case it’s contagious, when Remus tries to pass Harry to him. He comes up with excuses every single time. He lies to Lily, to James, to Remus, Peter, Mary, Marlene, Dorcas, Emmeline, Frank, Alice, and everyone else who comes into contact with Harry and him.
Everyone, after two months of this, assumes that Sirius just doesn’t like babies and isn’t willing to say it to them, for some reason. When James finally corners him, handing him Harry because “he’s your godson! You can’t go your entire life avoiding him. How do you expect to bond with him if you won’t even let him hold your finger?” Sirius awkwardly holds the kid, every muscle in his body tense, tears in his eyes, shaking, genuinely petrified. James takes Harry back and finally presses Sirius until he spills.
Sirius adores Harry. He doesn’t love kids, generally, but his nephew, his godson, is the exception. That doesn’t change the fact that he is terrified of the idea of hurting Harry. He’s so scared that his upbringing has permanently fucked something in his brain up and, if he gets into close contact with a kid, that something will be triggered. He’s terrified that he, if presented with an innocent, sweet, adorable child, could become the monsters that raised him.