Growing Up
Disclaimer: I'm just using them for my own desires.
When it came to pranks, girls, or things that involve being immature, Sirius Black was the best. He was only rivaled in this department by his best mate, James Potter. That was until recently. Before James decided to do a thing Sirius would never dream of doing, growing up.
It all started when James developed feelings for Lily Evans and she didn't return them. Confused by how a girl could possibly be disgusted by him, James tried several things to win over Lily. But time and time again, he would get the same reply to his advances, "No, not even if you were the last boy on Earth!!"
Sirius felt bad for his friend, and so did Remus and Peter. They constantly provided moral support and little snippets of advice to ease the confusion and hurt James was going through. This didn't help much, but he was always grateful for his friends being there for him.
He began to cool down a bit in sixth year when it came to being arrogant and a show off in front of Lily. She and his friends all noticed the change in the raven-haired boy. Lily in turn began to stop shunning him as much as she once did and started to have civil conversations with him.
At the beginning of seventh year James had changed his ways significantly. He no longer played pranks on unsuspecting first years, tortured Snape, ran his hand through his hair, and most importantly, he stopped asking Lily out several times a day.
As if this wasn't surprising enough, he had also been made Head Boy. Most were cowed by this decision by their eccentric Headmaster, but James handled the mantle quite well. This was again noticed by his friends and Lily.
One month into the new school year James asked Lily to the upcoming Hogsmeade visit and she said yes albeit with a bit of reluctance. Their first date went well and ensured many more in the future. During this time Lily realized she was developing feelings for the boy she once professed to hate.
James was happier than Sirius had ever seen him and this in turn made him happy. However his happiness was bittersweet. While he was glad his friend had finally gotten his dream girl, he also missed the old, immature James Potter.
He wanted to go back to the days where he and James would sneak off to the kitchens together in the middle of the night to visit the house elves or play an elaborate prank on the scummy Slytherins. Those days were gone and he would just have to except the fact that his best friend finds his new girlfriend to be more important than being childish.
At least that's what Remus tells him. Sirius just did not want to except the fact that maybe growing up was the best thing to do at that point. Especially with the war against Voldemort escalating to dangerous levels and the fact that he and the others had joined the Order of the Phoenix to help defeat him.
So as James continued to become more mature, responsible, and closer to Lily, Sirius continued to act like a young fool.
Three years passed and Sirius watched his best mate marry Lily Evans as his best man and had seen James' happiness grow even further. He was now with his friend as his wife was giving birth to their first child who was to be named Harry James Potter.
Sirius was almost as happy to be adding a new Marauder to the group as James was happy that the baby looked like him but with Lily's green eyes. Lily would not hear any talk of her baby boy being a troublemaker and scolded Sirius accordingly. Laughing at the look on Sirius' face when she explained why Harry would never play a prank, James told his friend that they had made him godfather.
Sirius looked to Lily making sure this was true and she nodded giving him a kind smile. He was excited by this declaration and did a strange victory dance in the middle of the hospital and was promptly told off by a mediwitch that eerily resembled the stern Professor McGonnagal. Lily and James laughed good-naturedly at their friends antics and began discussing what Harry would be like when he was older.
Even while seeing all the joy that James had gained from being more responsible and having a child with the woman he loved, it still did not occur to Sirius to do something that would probably make him happier. Growing up. So once more he continued to be a young fool who was often to rash in battle.
It was the Halloween of 1981 and Sirius learned that James and the whole Order had been betrayed by Peter Pettigrew. As Sirius flew his flying motorbike to the Potter's home in Godrics Hollow, he berated himself for trusting Peter with something as important as keeping a secret from Voldemort.
He wouldn't allow himself to think that he couldn't have known Peter would turn on them like he did, it would be unforgivable to try and excuse himself for not remaining their secret keeper. It had seemed like a perfect plan at the time and James had agreed. But look at what their trust had earned them.
As he drew near to his destination, tears welled up in his eyes as he took in the devastation Voldemort had unleashed on the Potter home. There was no real structure left, it was just a pile of wood and rubble. He dug his way through the rubble only to find the thing was dreading to see.
He looked into the lifeless eyes of his bet mate and began to weep freely. Looking around he saw Lily, somone he had come to love like a sister, lying on the ground about ten feet away from James. His tears began anew as he thought how he would never hear their voices again, laugh with them, or even be scolded by them.
Drying his eyes he began to search for his godson's body. While he was looking he heard an infant crying out. He immediately spotted the source of the crying lying in what remained of a crib. Sirius sighed with relief that at least Harry had survived this tragic murder. This left Sirius to wonder how when he spotted a lightning shaped scar on the baby's head.
Passing it off as a cut from the building collapsing, Sirius wrapped little Harry in a blanket he found. Sirius was startled by a giant man walking up to him crying. It was Hagrid coming to recover Harry and take him to Dumbledore.
Sirius obliged by giving him Harry and offering the half-giant his flying motorbike to take Harry on. He watched as Hagrid flew off with his godson to take him to somewhere brighter than this dreary scene.
The black-haired man looked once more at his fallen friends and resolved to get revenge on the rat that caused this. With an expression that was filled with venom, Sirius Black set out to kill his former friend. From that day forward, the newly admitted prisoner of Azkaban, did a little thing called growing up.