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He looked happy. Sirius looked happy. Maybe to most people he always did. He seemed like he never took anything seriously, that every inconvenience was just an excuse to make a joke, that everything came easy to him. Regulus knew the truth. He knew every expression of his brother's face and what was hidden behind it. He had seen them all.
He had seen him scared. He had needed time to understand why Sirius was scared, especially when Regulus was the one who had done something wrong. Then he had seen Sirius take the blame for him, or be loud enough to distract their parents. He had seen the rage in his mother's eyes, and he had understood.
He had seen him playful. Usually when it was just the two of them, alone in a room, Regulus trying to understand the rules of the new game Sirius had invented. It was alright if he didn't get it because it only made Sirius laugh.
He had seen him angry. At their parents, but at his brother too. He hated it, but he knew less and less how to avoid making him angry. He couldn't do what Sirius expected him to do. Obeying seemed safer, and Regulus was longing for safety. He wasn't brave like Sirius. Nowadays it seems like the only way to have his brother acknowledging him was to make him angry.
He had seen his fake smiles. Usually followed by the phrase "It will be okay". These few words always made Regulus shiver. That's what Sirius said before he left for Hogwarts. He had had a huge smile on his face, but Regulus could see how fake it was, could see the uncertainty in his eyes. But he was going away, he had no reason to be scared. Regulus was the one staying behind after all.
Now he saw him happy, truly happy. He saw it all from afar. He had new brothers, and a few friends around him too. He wasn't alone anymore. He didn't need Regulus. And then there was Remus Lupin. Regulus had suspected for months. He knew every expression of his brother's face and what was hidden behind it. He knew this boy was special, but hadn't understood how much until he saw them kissing near the quidditch pitch. Sirius was radiating happiness, and it only grew stronger with time.
Most of him wanted to reject the idea, wanted to throw a fit, wanted to tear that boy away from his brother. He knew that it should be shameful, hidden, that it should feel dirty and wrong. But it didn't, because Sirius looked happy, truly and completely. Regulus felt stuck, torn between what he had been taught and what he felt, which was the case more often than not. He wanted to be repulsed, but he couldn't.
One day, after he had been woken up early by a nightmare, he sat alone at the breakfast table. He felt colder and more alone than he had felt in months, he was longing for… something. He couldn't even pinpoint what. Warmth? Comfort? He didn't know. Despite his best efforts, his eyes always drifted back to his brother. In his defense, there was no one or nothing else that could distract him, and Sirius was in his line of sight. It was surprising, considering he wasn't usually an early riser.
He wasn't alone, Lupin was there too. They both looked tired and like they'd rather be anywhere else. Yet they were smiling at each other. They sat so close that it was impossible to say where one ended and the other began. Sirius was talking, Lupin was laughing, Sirius moved to make some toast before sliding the pieces towards Lupin, while he put an arm around Sirius' back. Regulus could see his hand moving in a comforting way, and then he understood. Maybe Sirius was longing for safety too. Maybe once the playfulness Regulus brought out was no longer in reach, Sirius had been left with the fear, the anger and the fake smiles. Maybe Remus made him feel safe and playful and happy.
Regulus tried to breathe. He felt heartbroken, without really knowing why. He had lost his brother a long time ago, but maybe it only sinked in now. Sirius would be okay, he would be okay, and happy, without Regulus. Relief and hurt were fighting in his throat. Sirius deserved the happiness, Regulus only wished he could be a piece of it too. But it was too late.
The Great Hall felt suffocating. He left everything in place and all but ran for the exit, conscious that he had nowhere to run to. He'd find something, somewhere, to hold onto, something that wasn't his brother. He had to.