A/N: It seems to me like Sirius, in part, found the courage to first be sorted into Gryffindor, and then to leave his family behind forever, from Andromeda. Andromeda, in turn, found the courage from Ted Tonks. This is a tale of two stories, starting at the same place but taking radically different paths.
Note: I couldn't find anything on whether Ted Tonks was, in fact, a Hufflepuff, but I've seen him as such in so many stories that I wrote him as one.
Note Number Two: The second "path" leads into canon, so it is much less detailed and much shorter than the first.
All characters and settings belong to J.K. Rowling.
Sirius had always been his cousins' darling. Andy, Bella, and Cissy used to sweep down on him and carry him off as soon he arrived at their house or vice versa. They would dress him up, play hide-and-seek, and generally spoil him. Occasionally, if they needed another player in their elaborate games, Regulus would be invited, but most often it was Sirius and his cousins.
He wished they were his sisters.
As each of them left for Hogwarts in turn, they wrote him every week. When he was seven, watching Cissy board the Hogwarts Express, she made him a promise. Laughingly, carelessly, she said, "You'll be eleven before you know it. Bella will be gone by then, but Andy and I will still be there, and we'll have fun. You'll be in Slytherin like us, and we'll run the whole school!"
It sounded too good to be true, but it wasn't. When he arrived at Hogwarts and was sorted into Slytherin, Bella was in the midst of planning her wedding to Rodolphus Lestrange, but even she still wrote him weekly. Andy and Cissy were the perfect connections – both stunningly popular in Slytherin House, both willing to let him tag along with them until he had gathered his own circle of friends – or rather, allies.
Malfoy, Avery, Mulciber, Rosier, and Wilkes. These were his loyal associates. However, life was not all idyllic for the boy who was regarded by many as the Slytherin Prince. There were those who hated him. A small group of blood traitors and half-bloods in Gryffindor had made it their mission to disturb his peace.
James Potter was the only one worth trying to salvage out of the group. He could have been every bit as popular with the right crowd as Sirius himself, if he tried. However, Sirius's perfectly friendly attempts to get Potter to see things in the proper light while there was still time – on the Express – had been met with impolite rebuffs.
Sirius was also concerned with his housemate, Severus Snape. Snape was a half-blood, but he was almost worthy of associating with Sirius and his crowd. Unfortunately, the boy seemed too busy mooning after some Gryffindor Mudblood than trying to atone for his impure blood. Sirius shrugged it off. He knew that blood would always tell.
When Regulus started school, he coasted along on Sirius's coattails for a time, much as Sirius had done with Andromeda and Narcissa. In time, however, he gained his own place in the Slytherin social structure. He would never be as popular as Sirius, but neither was he shunned. He was a respectable son of the Blacks.
In Sirius's fifth year, Severus finally straightened things out as far as blood purity was concerned. After their OWL's, when the Mudblood Evans started dating the blood traitor Potter, Sirius noticed a definite improvement in Severus's attitude. He approved.
At Andromeda's wedding to Walden Macnair, Bellatrix pulled Sirius aside and told him, in detail, about the Dark Lord.
Sirius was thrilled.
He and his cronies all received the Dark Mark as soon as they turned seventeen.
Sirius had always been his cousins' darling. Andy, Bella, and Cissy used to sweep down on him and carry him off as soon he arrived at their house or vice versa. They would dress him up, play hide-and-seek, and generally spoil him. Occasionally, if they needed another player in their elaborate games, Regulus would be invited, but most often it was Sirius and his cousins.
He wished they were his sisters.
As each of them left for Hogwarts in turn, they wrote him every week. When he was seven, watching Cissy board the Hogwarts Express, she made him a promise. Laughingly, carelessly, she said, "You'll be eleven before you know it. Bella will be gone by then, but Andy and I will still be there, and we'll have fun. You'll be in Slytherin like us, and we'll run the whole school!"
It sounded too good to be true, and it was.
When he was ten and Andy was sixteen, she pulled him aside during her Christmas holidays.
"Sirius, I've got something important to tell you." She took a deep breath and went on. "Don't listen to them. Muggleborns and half-bloods are just as good as purebloods."
He was shocked, and seriously considered running to his father to tell him of Andy's blasphemy, but she had always been his favorite cousin, so he heard her out. She told him everything she knew, courtesy of a Muggleborn Hufflepuff friend of hers, about the Muggle world. Instead of being disgusted and repelled, like he knew he should be, he was fascinated.
From then on, Andy's letters changed. Instead of informing him on the latest pureblood exploits, she told him about adventures that she and her Muggleborn friend, Ted, had. She and Ted met in secret, no more than once a week. The rest of the time they sent notes back and forth.
Andy's letters had the effect that she desired. Instead of growing cold and calculating, as most pureblood children did the year before they attended Hogwarts, Sirius remained the warm, happy little boy she had played with. She knew that his parents were worried about him, as both she and Cissa had received short notes asking for them to watch over him especially when he arrived.
She planned to.
She couldn't have been more thrilled when he was sorted into Gryffindor.
A/N: In my version of events for Slytherin Sirius, James and Lily's story goes like this. James was less of a prat without Sirius there egging him on, so Lily was never as violently opposed to him as she was in canon. After OWL's, James did something nice for Lily, and she agreed to go out with him. Severus never called her a Mudblood. I'll leave it up to you as to whether he was a spy for Dumbledore or not.
Incidentally, Remus would have been the Potters' obvious choice for a Secret-Keeper (he was James's best friend) in place of Sirius, but I never got around to deciding how exactly Halloween would have played out.
Sirius was involved in the attack on the Longbottoms and sentenced to life imprisonment along with the Lestranges and Barty Crouch, Jr.