He'd never told anyone, but Bellatrix was always his favorite cousin. He said Andromeda was because she got away from all the pureblood nonsense as well, but it was Bellatrix. He loved Andromeda for her beliefs, yes, but in personality? Bellatrix always took the cake on that one. She was eight years older than he was, so maybe it was just that he idolized her when he was younger and so he'll always have this slightly tinted vision of her.
Bellatrix was wild when Andromeda was moderate and Narcissa was calm. She was beyond embarrassment, aching to go out and set fire to everything she laid her eyes on. That was how he wanted to be. He wanted to be the one making the remarks that shut everyone else up. He wanted to be untamable; the one you couldn't tell what to do. He wanted people to have that look that was made of half fear and half respect that Bellatrix received whenever she walked into a room. She was severe and wild, unmanageable at the best of times.
She was the first to speak to him at a function their family was hosting after he was sorted into Gryffindor. She practically flew over to him, her hair swinging behind her when she first spotted him. He couldn't quite recognize what her expression was, but she smiled slightly at him. "Perhaps there's still time," she whispered to him. He spent the rest of the night trailing behind her as she introduced him to all the people there.
The only relative who wrote him while he was at Hogwarts was Bellatrix. He couldn't read half of her writing, but she seemed interested in keeping up with him and who was in contact with. He got at least one letter from her every year, though she sent more when he was in the lower years. She even wrote him after he'd been blasted off the family tree, though those were mostly pleas for him to see reason and come and talk to her.
Another thing was that Bellatrix came and found him two weeks after he'd run away. She hadn't entered the Potters house, but she'd sent an owl up to the room he was staying in with a quick message scrawled on it. Come into the yard and talk to me. He knew who it was from, and he knew that he shouldn't. He went anyways.
"No wonder you were sorted in Gryffindor. You called your mother a hag, and then you ran away from home. Yes, because stating one's opinion and running away if rather brave of you, isn't it?" she'd mocked him, leaning against a tree. "You've gotten yourself blasted off of the damn family tree, Sirius. That's not something you can go apologize for and expect for her to forgive you of!" she cried louder, shaking her head slowly at him in disbelief.
He remembered being offended at the fact that she thought he'd regret it later on. "I'm not going to apologize for it! I'm not going to apologize for any of it! I'm not sorry I got into Gryffindor, and I'm not sorry that James is my best mate! I'm not sorry that I'm not a Death Eater either! You don't understand; I don't want to be sorry for any of it! I'm not going to apologize. You can't make me," he said forcefully, confused by her sudden laughter.
Laughing, she titled her head back against the tree and let the peals of laughter echo around them. "You don't think I could make you?" she asked once she was calm enough. "Have fun playing the hero while you run away from everything that matters in the world. And no, I won't tell you mother that I've seen you," Bellatrix tacked on at the end, smiling at him with the smile others shied away from. Sirius ran full force at it, not even attempting to back away from the challenge she'd left unspoken.
"You can tell my mother anything you want to. I don't care about what she has to say!" he yelled angrily. "Why is it so important that you have to come and find me? You're just using me for a cause that's not going to go anywhere! I hate you!"
Her eyes had turned wild and her sneer vicious. "You think the Dark Lord's cause is going nowhere? You're the one that's going nowhere. You're the one who will never go anywhere. You're too stupid to see real greatness!" she cackled, raising her arms above her head as if to emphasize her point. She froze though, and then smile gravely at him, her eyes as sane Bellatrix ever got. "But hatred? That will get you somewhere." She'd whispered it maliciously before Disapparating.
It was the last time they'd spoke on civil terms. But as much as he hated her, he wanted to be here more than anything. More than everything.