Disclaimer: I own exactly 0% of these characters. You may not have seen some of them in the books, but they are a part of the Black family tree and I am only borrowing them to amuse myself.
Sirius Black in Azkaban!
Arcturus Black stared at the headline of the Daily Prophet with undisguised shock. There was a large picture of his grandson below the four-word title, depicting Sirius laughing madly as he was hauled off by Aurors. The dead muggles that littered the street seemed irrefutable proof that his grandson, his heir, was a convicted mass-murderer.
"Father," a familiar voice interrupted his thoughts. Arcturus glanced up to see his daughter standing there, her brow knit in a frown.
"Is it true?" Lucretia asked quietly. "Sirius is a Death Eater?"
"It would seem so," Arcturus muttered, looking back down at the article.
Lucretia shook her head, sliding into the chair across from him. "But it makes no sense. Sirius hated the Dark Arts with every inch of his being. He was a Gryffindor, he was friends with muggle-borns and half-bloods, and he fought again You-Know-Who! And James Potter was his best friend, why would he betray him?"
Arcturus rubbed a hand over his face. "Lucretia, I have no idea what goes through Sirius's mind. Perhaps he really did become seduced by the Dark Arts, enough to turn traitor. But, I admit, it seems unlikely."
"It is unlikely!" Lucretia, who had always had a soft spot for her wayward nephew, had raised her voice. "You know Sirius, Father; he'd never do something like this! Never!"
Arcturus merely stared at his daughter, who slowly calmed down enough to lower her voice. "Father," Lucretia said softly, "would it be too much to ask for you to investigate this?"
Her father considered. "No, Lucretia, I don't think it would be too much to ask."
"What do you mean there is no trial arranged for my grandson?!"
Arcturus's furious voice echoed in the small office, making Crouch wince. "Sir," Crouch began, but Arcturus cut him off.
"Is this a sign of disrespect to my family, Crouch?" Arcturus's voice had lowered dangerously. "That you think Blacks are not good enough to receive fair trials? That we are all automatically evil and not worthy of your attentions once they have been chucked into prison? Would you like me to inform Sirius's mother of the insult to her son? Everyone else accused of being Dark gets a trial—why doesn't Sirius?"
"Mr. Black, please!" Crouch, well aware of the political clout Arcturus held, was nearly begging by now. "We will arrange a trial as soon as we can. We do have many others already lined up, but we will fit your grandson's in as soon as we can."
Arcturus stared at Crouch a moment before withdrawing a small bag from the pocket of his robes. "How soon is 'soon'?"
Greed crossed Crouch's features and he quickly snatched up the bag of galleons. "Sometime next week, I would say," Crouch smirked.
Arcturus raised an eyebrow. "Good. Don't change your mind." He turned, and walked out of the office, intent on paying a visit to his grandson.
Silver mist slowly solidified into the form of a snake, curling around Arcturus to warn off the dementors that swarmed nearby. Keeping the memory of his wife and children in his mind, Arcturus walked through the wall of dementors, which parted obligingly in fear of his patronus, granting him access to his grandson's cell.
"Sirius," Arcturus said, using the tone of voice that had always made Orion and Lucretia jump to attention. It worked like a charm, and Sirius, who had presumably been hidden in the shadows at the back of his cell, came forward to face his grandfather.
"What are you doing here?" Sirius's coherency gave Arcturus some relief that the dementors had not done much damage yet.
"I have arranged a trial for you, Sirius," Arcturus said matter-of-factly. "It will take place next week. However, there is not much difference a trial can do if you are truly guilty of mass murder."
Grey eyes met grey, one pair furious and one pair calm. "I'm not," Sirius said through gritted teeth. "I can prove it with Veritaserum."
"Then I will see to it that you are granted Veritaserum," Arcturus said absently, focused on the nonverbal magic he was doing. "Can you give me the story now, though?"
Sirius snorted. "I'll give you the story if you give me some credit, Granddad. I know you're trying Legilimency."
"And yet you make no effort to stop me," Arcturus pointed out, sounding distinctly unsurprised.
"If it gets me out of here, do what you want," Sirius told him. Arcturus had the impression that, had this been under any other circumstances, Sirius would not have been nearly so accepting.
"Very well." Arcturus leaned forward, grabbing hold of the bars to support himself as he did so. "Open your mind fully, then."
Sirius obeyed, and the story suddenly made sense.
"Where's my godson?"
Arcturus raised an eyebrow, amused, as Sirius confronted Albus Dumbledore mere minutes after he had been acquitted. The crowds of people that had attended were far too busy whispering amongst themselves to pay much attention to either of the two men, leaving them to talk in relative peace.
"Sirius, I assure you, Harry is safe," Dumbledore said reassuringly. "I placed him under only the strongest protections."
"I want him back," Sirius said flatly. "I am his legal guardian, not whoever you foisted him on."
"Headmaster," Arcturus interrupted, striding forward to reach the two men. "I do believe Sirius makes an excellent point. Harry Potter cannot legally be under anyone's care but his, unless Sirius chooses to give him to someone else—and he has not. It would be in your best interests to allow Sirius to take his godson back."
Dumbledore was aware that he was outnumbered, but he held his ground. "Sirius, I put him under blood wards—"
"If you recall, Headmaster, my father researched wards for the Department of Mysteries," Sirius interrupted. "I have any number of strong, unbreakable wards I can use to protect Harry at my disposal."
"Out of curiosity," Arcturus added, "who is this blood relative you put Harry with? Sirius and James are distantly related, which may be enough for the blood wards."
"No, it has to be Lily's blood," Dumbledore countered. "She is the one who gave her life defending him."
Sirius's expression had grown stony. "You gave him to Petunia," he said slowly. "My godson, to magic-hating muggles."
His anger was easily spotted; Sirius was on the verge of exploding. Dumbledore seemed to recognize the danger. "Sirius," he began, but was cut off.
"I want him back," Sirius hissed. "And I'm sure I can find out where Petunia lives. Have a good day, Headmaster."
He stalked off into the crowd, ignoring all the reporters who called out to him. Arcturus was sure that Sirius's destination was Godric's Hollow, where the widowed Charlus Potter could tell Sirius where his daughter-in-law had lived.
"You really didn't have a chance of stopping him anyway," Arcturus informed Dumbledore conversationally. "He's a Black, after all."
Dumbledore sighed. "Black, indeed. He takes after you, I would think."
Arcturus smirked. "Yes, I would think he does."
"Aunt Lucy!" Sirius called out in greeting, breezing into the living room of his aunt's house.
Lucretia looked up and beamed at her nephew. "Welcome back, Sirius," she said, drawing close enough to catch sight of the sleeping, dark-haired infant in Sirius's arms. "And this would be the Boy-Who-Lived, I assume?"
Arcturus watched them from the doorway for a moment before leaving them in peace. The fawning over Harry instantly stopped when he left, breaking the atmosphere of cheerful welcome.
"Aunt Lucy," Sirius said quietly, sitting down on a couch. "Did you have something to do with Granddad getting me a trial?"
Lucretia shrugged. "I suggested to him that he should investigate your arrest, but I did not expect to see you acquitted," she admitted. "Although, I am glad you were."
"Yeah, so am I," Sirius grinned briefly, cradling Harry closer. "But I never got the impression he was particularly fond of me. You and Uncle Alphard were the only ones who really were."
"Yes, but he did reinstate you as his heir, remember?" Lucretia pointed out.
"He had no choice," Sirius reminded her. "It was a choice between me and a Malfoy, and Granddad would never let this family line die out if he could help it.."
Lucretia laughed. "True. Maybe it's time to find yourself a girl who'll give him some more heirs."
"Maybe later," Sirius dismissed.
"I would prefer now," Arcturus interrupted, entering the room. "Although that is, of course, your choice. But may I point out to you that your life sentence in Azkaban would have been the end of my line had you not been innocent and acquitted."
"Good thing, then," Sirius grinned. "But my priority is taking care of Harry, Granddad. I'm not looking for a wife."
"I think you're both overlooking something," Lucretia pointed out. "If your line was extinct, Father, who would the Black family pass to first?"
"Bellatrix's sons, provided she has any," Arcturus, who was obviously well-versed in matters like this, answered immediately. "Then it would be Draco."
"And following that?" Lucretia pressed. "Maybe you need another look at the family tapestry?"
"No, I know what's on the family tapestry," Arcturus assured her. "After Pollux's line, it goes to his siblings. But Cassiopeia has no children, Marius was disowned, and the youngest is…"
"Dorea," Sirius cottoned on. "James's mother. And Harry is James's son."
"So, you could bypass Bella and Draco entirely and name Harry your heir without anyone being able to protest, because Harry also has a claim to the fortune," Arcturus concluded.
Lucretia smirked. "Just imagine Lucius Malfoy's face when he finds out that his wife's family's fortune will never get to his son."
Sirius started laughing, but quieted when Harry stirred and awoke, opening bright green eyes to blink sleepily at his godfather.
"How about that, Harry?" Sirius said softly, rocking Harry back and forth. "You're the new heir of the Black family."
Harry made a noise that could have been approval and curled into his godfather's chest, content.
Author's Notes: So, I don't normally dabble in alternate universes, but this plot bunny just wouldn't leave me alone. There are several things in this story that I think might confuse a few readers, and if you have any questions, please ask me in the review and I will answer ASAP via PM. I do have reasons for the personalities I gave Lucretia and Arcturus, and if you are curious, don't hesitate to ask.
Also, this truly is a oneshot. I'm not going to be updating it further. If, however, someone wants to take the idea and run with it, just ask and credit me. And if you liked the fic, please review and tell me so! Thanks!