Out of everyone in his family, Sirius reckoned that the most mystifying of the lot of them was his cousin Bellatrix. She was five years his senior, and from what he could tell she was quite a bit like him, with the exception of all the ways that really mattered in the end. He couldn't understand how it was that someone so like him could have views so different from his own, it simply didn't seem plausible. Sometimes he wondered if she felt the same about him.
Both Sirius and Bellatrix were people of action; they couldn't stand it if they were not the center of attention in any situation, regardless of whether it was negative or positive. Both had quick, fiery tempers, and neither was afraid to unleash them on whoever happened to be around at the time. Both could charm their way out of or into absolutely anything effortlessly; they were used to getting their way. Both were entirely wrapped up in their own beliefs and refused to listen to anything anyone else had to say, and both were considered brilliant, witty, and immensely talented in the art of magic.
However, they were so vastly different in every other aspect of their lives that these similarities were scarcely noticed; or at least if they were no one dared mention them to either party for fear of the inevitable outbreak of fury. Sirius believed that there was not a single difference between purebloods and muggle borns, except maybe generally speaking purebloods were a hell of a lot more high and mighty than their counterparts. Bellatrix was of the opinion that mudbloods were scum and had no right in such a prestigious place of magical education as Hogwarts; it was an insult to allow them to wander among purebloods as if they belonged.
So as they grew, Sirius became a Gryffindor and Bellatrix a Slytherin, and Sirius befriended the likes of James Potter and Remus Lupin whilst Bellatrix placed herself in the company of names such as Lucius Malfoy and Rodolphus Lestrange. Sirius was the "white sheep" of the family, and Bellatrix was the shining example of what the Black family name prided itself on. Later Sirius joined the prime ranks of Dumbledore's Order of the Phoenix whereas Bellatrix attached herself to the new Dark Lord Voldemort's loyal collection of Death Eaters.
Sirius laughed bitterly as he reveled in all the comparisons between himself and his "dearest cousin." In the end they had both ended up in the same place despite all his best efforts. He was in Azkaban and so was she, both resenting the other and both loathing each other for reasons neither would ever understand. She was absolutely furious that her blood-traitor of a cousin had illegitimately achieved the title of the Dark Lord's right hand man, a title that belonged to her. He vehemently hated even the sight of her for what she had become, nothing more than a murderous lunatic, obsessed with another man's ideals.
It was obvious that being a Black meant being a Black for life, whether you choose to be or not, whether you do all you can to rid yourself of the wretched name, or do your damndest to live up to it. In some convoluted way, all would come to the same sort of end, and it would never be a pleasant one. He knew that it wasn't fair or just or right that he should end up in the same place as his cousin, who he had strived to opposite his whole life, but he'd known all along that they were far too alike for that, that no matter what he'd have the same strengths and weaknesses as she did. It had always been rather obvious really, that they would become the same at the end of it all, he'd just never wanted to admit to that. The only consolation he held now was the fact that he had done all that was in his power to stop it, and maybe helped out a bit along the way.