Not all stories have a happy ending, or even a happy beginning for that matter. Sirius Black's story certainly didn't. The middle didn't go all that well either, but then again, the bits in between? Those were the best days of his life and it was all because of the Marauders.
James Potter. We all know about him and he certainly never changed, Lily might say he became a bit more mature, but in all honesty, he was the same as he'd always been. He still ruffled his hair, an annoying habit he had picked up in first year after first setting sights on Lily Evans. But all in all James Charlus Potter had to be Sirius' favourite person in the history of the world.
Remus Lupin. You may not know it from looking at him in the future, but Remus was quite the reckless prankster back in the day. He may not have picked on Slytherins or executed the pranks like Sirius or James, but he did come up with the finer details and find the appropriate spells. He was Sirius' moral guidance, the conscience that sometimes lay forgotten in the back of Sirius' mind.
Peter Pettigrew. He was the one who changed the most. Believe it or not, Peter Pettigrew wasn't always the selfish death eater he was now. In his Hogwarts days, the thought of betraying his friends made him physically ill. Sure he wasn't the smartest or the bravest out of the group, but no one could deny that he was loyal. He was a great friend. Sirius always did wonder what happened to change their little Wormtail into…well…a traitorous rat.
These three may have main roles in this story, but that's not who it's about. This is Sirius Black's story, and I have to warn you, it's not entirely happy.
In 1971, the Marauder's first year, when asked who knew Sirius the best, the answer was obvious. James Potter. And that was true…then. In 1972 to 1974, they would give the same answer. James Potter. And that was true…then. But in 1975, that's when things would change, when asked, they would say, of course, James Potter. But they would have been wrong, during Sirius' fifth year the person who knew him best was his brother, Regulus.
The reasoning behind this was a secret, that none would uncover, well not yet anyway. While James may have known Sirius the best in his first four years at Hogwarts, that doesn't mean he knew him completely. Sirius was always a brilliant actor.
So in Hogwarts when asked to describe Sirius Black, it was obvious they would all say exactly what Sirius wanted them to. Reckless, egotistical, a prankster, always happy, but most of all, he never breaks, he always stays strong. But, beneath the surface? That's not true. Sirius planned for no one else to find out the fact that he is actually filled with self-loathing and at times he was downright depressed, but when do plans ever work out? Harry Potter certainly knows all about that, but we're getting ahead of ourselves, this isn't Harry's story.
As I mentioned before, Regulus was the first to discover Sirius' secret, as despite what other's thought, the brothers actually did love each other and when that secret Regulus found out what Sirius was hiding, they had an unbreakable bond.