A Different Set of Rules

I don't own 'Harry Potter'

Warning: slight underage (sort of?)

"Look, it's him!"

"The Heir of Slytherin."

"A Lord twice over, you know."

The boy – man, really – tried not to sneer as he stalked the halls of Hogwarts, ignoring the gawking and whispering of his fellow students. They really were a bunch of hypocrites, running their mouths about propriety and traditional etiquette, yet quickly degrading into uncouth teenagers without a shred of shame in their bodies.

Harry knew he sounded cynical but life had fucked him over too many times to care at this point.

After living a miserable life married to a fangirl, children who seemed to think he was a horrible man for divorcing the cheating bitch, and a job that killed him from the inside, he'd thought death would have been a reprieve. There was just one thing he forgot.

He was Harry-fucking-Potter, and the Potter luck lived to screw him over.

Waking up in the body of some poor kid in a shitty orphanage made him want to scream, especially as his life was disgustingly similar to a young Tom Riddle's. Realising that he was eleven in the year nineteen nine was simultaneously infuriating and intriguing. The possibilities to stop certain things from happening had been too good to pass up, especially with his new body.

Cadmus Thanatos Peverell.

Firstly, the world could go fuck itself, and secondly, why couldn't wizards give their kids normal names for once?

Cadmus Peverell, undisputed king of Slytherin House (he didn't manage to talk the hat down twice), one of Headmaster Black's favourites, Lord Peverell, and Lord Gaunt. He was rather grateful that he'd dealt with having a fuck ton of betrothal contracts thrown at him before or he wouldn't have been able to deal with it.

Not that he was going accept just anyone. He actually did want a spouse and children to pass his titles on to, but nobody stood out enough for him to pursue.

His musing was cut off as a smaller body collided with his, and Cadmus' arms came up automatically to stop the younger boy from falling. He watched as the head tilted up and the boy apologised graciously, but he was captivated by the eyes.

Sirius' eyes.

He was holding onto Arcturus Black, Sirius' grandfather. The man in front of him had grown up to be the perfect Heir then Lord Black, even if he'd all but ran away to France after the war because his wife had died and his family had been falling apart. He hadn't had the best run as Lord Black, only inheriting after his father had made some truly atrocious decisions, like the marriage between Walburga and Orion.

The fourteen-year-old Arcturus wasn't even Heir Black yet, he had a little baby fat on his cheeks, and there was an innocence to the grey orbs that he hadn't ever seen in Sirius'. Could he really do it? Could he let the Black family play out in the same tragic manner as the future? Cousins marrying each other, killing each other … Sirius growing up as Walburga Black's son.

Fuck no.

"There's no need to apologise, Master Black. It was an honest mistake."

He smiled gently and inwardly smirked at the light red flush suffusing the pale cheeks. The boy was striking like the rest of the Blacks, and the suddenly shy demeanour made his stomach clench with desire. He knew full well he was probably a little twisted; Arcturus was fourteen, not to mention part of Cadmus' attraction stemmed from how much he resembled Sirius, the man he'd grown up having inappropriate feelings for.

There were two options available to him. He could allow this man to get married within the next few months to the former Hufflepuff Melania Macmillan, a simple girl who would never fully bond with her in-laws, an outcast light witch among the dark Blacks, or he could present Phineas Nigellus Black with an offer he really couldn't refuse.

There was no choice.

"Master Black, you wouldn't happen to be betrothed at all, would you?"

The boy cocked his head, eyes narrowing. "No. Why?"

Cadmus leant in, leaving barely an inch between them and whispering, "Would you like to be?"

Red painted Arcturus' face and Cadmus smirked lazily, keeping silent as he waited for the boy to process his offer. He wouldn't force him, but he could certainly entice. Grey eyes were wide, darting from side to side even as the teenager squirmed where he stood, no doubt imagining something illicit. Eventually he nodded cautiously, a delightful red still sitting high on his cheeks.

"Excellent. Perhaps we should take this to Lord Black immediately."

Standing in front of a satisfied looking Phineas Nigellus Black, the boy at his side still enticingly flushed, Cadmus could almost feel the future rearrange itself around him.

If one thing was certain, it was that he was going to play by his own rules this time.

A/N: Hello guys!

I've never thought about this pairing until I got a request over on AO3 (shoutout to misschief_managed), but I have to admit it has potential, and I'm now thoroughly intrigued lol

Hope you like it, and happy reading :D