Family.
When Regulus was sorted into Slytheryn, Sirius felt relief. And when Regulus ignored him, Sirius felt torn open inside.
Not having his little brother, who was the only person he had for 10 years, even acknowledge he exist, hurts more than he could put into words.
...
Sitting up in the Astronomy tower after curfew was peaceful, it was quiet and allowed Sirius to breathe, he didn't have to pretend here.
Sirius didn't really pretend with his friends, he could be himself with them, his real self. It's hiding the ugly sides of him that make him pretend.
Sirius could sit here and look at the stars for hours, that's the only way he could communicate to his twin star.
He didn't have to look to know it was James walking into the Astronomy Tower, he could hear it, he got good at that. "Sirius? Why are you up here alone after curfew?" James said, curious but obviously tired.
"I'm looking at the stars" Sirius said softly, smiling just a bit when James came and sat next to him. "The stars are pretty" James said, it sounding like a mere hum.
"They are, did you know me and my brother are named after stars?" Sirius responded with, James shook his head. Sirius pointed at a star, bright and easily noticed, "That's the dog star, the star i was named after." Sirius said before shifting his hand to point at another star, fierce and pronounced, "That's the star Regulus was named after. In latin it means Little King, the heart of the Leo constellation." Sirius said fondly.
"They look like twin stars" James commented, adoring how Sirius softened when talking about his brother.
...
"Reggie, that's the star you were named after!" little 9 year old Sirius said as he pointed at the star. "Really? That's so cool!" little 8 year old Regulus said in awe as he stared up at the sky.
"Look Siri, that's the star you were named after!" Regulus said, pointing up at the star. Sirius chuckled, "They kinda look like twin stars, their just like us, twin stars Reg" Sirius commented.
"Will we always be twin stars Siri?" Regulus asked, looking at Sirius with those eyes that softened Sirius to jello, he'd do anything for his brother, he will do anything for his brother, no matter the cost.
"Always Reg."
...
"Yes they do" Sirius said quietly, his heart aching for his other twin star. "Regulus is my twin star" He said, it was fondly, it was like he was longing for his brother.
James frowned slightly, he didn't know if Sirius and Regulus had been fighting or not but he didn't like how sad Sirius sounded, so he wrapped and arm around his shoulder. "You guys are brother, and sometimes stars drift apart, but not for long." James had said.
Sirius smiled slightly leaning into James, James always knew how to comfort people, he was always so warm and kind Sirius thought he'd always have James warmth to keep him warm even on the coldest of nights.
Neither of them knew of the 14 year old on the stairs, that heard everything. Oh how Regulus yearned for his twin star to.
...
The next day, Sirius, James, and Peter all were excited to show Remus. All 4 of them sat in their dorm, playing a card game when the 3 decided it was time.
"Alright Alright, pause the game." Sirius said, setting his card down and waiting for the other to do the same. He looked at Remus witha huge grin, "We found a way to be there for you at the shack during full moons" Sirius said.
Remus nearly fainted at the idea of these 3 idiots being in the shack with him on full moon nights. 'They found a way'? Don't joke with him. "No you didn't" He said, still a bit in shock at how stupid they could be.
"Did to! Listen, Werewolfs only attack humans because werewolfs see them as a threat. Butttttttttt they don't attack animals." Sirius had said cheekily. Remus could have sworn he fainted, please don't tell him they did something stupid.
They did something stupid. "What do you mean you 'became animagus's'! We're 15! It's illegal and you'd be unregistered which is also illegal, so i doubt that. And what do you mean you don't know what they are if you did actually pull it off, wouldn't you lot be like, to excited not to know" Remus said, clearly not wanting to deal with their bullshit right now.
"Peter, go first" James had said and ushered him. "What! Why m-" Peter exclaimed and of course Sirius cut him off, "Don't do the 'why me' bullshit just hurry up!" he said impatiently.
Peter grumbled but complied, Remus must have been seeing things because now in Peter's place was a rat. A rat for crying out loud!
"Peter's a freaking rat?!" James said incredulously, "Well i'm not all that surprised" Sirius commented offhandedly and James elbowed him in the side causing him to wince and grumble as he rubbed his side.
"Okay Okay, my turn" James said with a grin so bright the other 3 almost went blind. Remus blinked and there was a stag in James place, a stag! All he did was blink!
"Holy shit your tall!" Sirius said in awe looking at James. "Stags are supposed to be brave animals so it makes sense" Peter had commented, Sirius was to distracted by James to even notice Peter had reverted back.
"Alright now for the main show, my turn!" Sirius said, sounding way to cocky for this. James was back as, well, James, Remus couldn't explain it so he watched Sirius, this was all a lot.
Mere seconds later there was a black dog licking James face, licking his face for Christs sake! Sirius was huge to, a huge Black dog that was Sirius, oh what a fuckinghandful.
"Sirius enough" James laughed, trying to get Sirius to stop licking his face. Sirius complied and sat down, and then he was back as Sirius seconds later. Dear Merlin Remus felt like he just got told his kids were suspended, i'm too young to be a dad already, he thought.
"We should come up with nicknames to match our dear Moony" James said, smiling. "Yes! Peter should be Wormy- no Squeaks- wait no Wormtail!" Sirius said, already having ideas in mind. "Then your gonna be Padfoot!" James said, looking at Sirius with that grin that made Sirius warm. "James should be Prongs" Peter said.
Remus was in awe, his friends did this for him, and then came up with nicknames to match him. He loved them, these people were his family.