Regulus had always wanted a brother. (A sister wouldn't have been too bad, either, but if he could have had a sibling, and could have chosen, he would have picked a brother.) He used to ask for a brother from his parents when he had been younger, but he had stopped when it had only served to annoy them.
Orion and Walburga disliked children, and they were happy to have only one. They told Regulus to stop wanting something that would never happen, and to accept his cousins as his friends and playmates; but Regulus didn't like his cousins and avoided them whenever they came for a visit, because they were mean and looked down on him with disdain, as he was the youngest one, the lonely one, and easiest to bully.
When Regulus was eight years old, he had got used to being alone. He had almost forgotten his longing for a brother.
And, then, he got one.
The brother was small, but not as small as a baby. He was but a little toddler, with the same pitch black hair as Regulus. He looked up at Regulus from the floor with his pale eyes, somehow looking serious and older than his apparent age, as their mother introduced them to each other in the middle of the night, in the flimsy light of a wand, after waking up Regulus.
His name is Sirius, their mother told Regulus, in hushed delighted whisper, and Regulus remembered how the wand's light had glinted off their mother's new golden ring, heavy and thick on her left hand. He is your brother.
Regulus had looked back at Sirius, and he had wondered, and had almost asked his mother why they had changed their minds about a second son, but something had stopped him.
He had finally gotten what he had always wanted, so why question it now?
He had hugged the little boy before their mother took Sirius away from his bedroom, and Regulus had gone to sleep with a smile, thinking of all the things he'd show to his new little brother the next day.
At first, it was the best thing that had ever happened to Regulus, to have his silent and agreeable brother by his side. Regulus showed him around their home, a maze of a house which had belonged to their family for centuries. He showed Sirius all the paintings of their haughty ancestors and whispered to him the horrific stories he had been taught about them. He told Sirius about the great-great-uncle, who had been eaten by the demon he had summoned. He told him about Aranea, the greatest warlock of her time, who had been caught by the church and burned in the capitol, and whose daughter, Sagitta, had burned the priest's family alive in revenge. Sirius listened to Regulus' stories, never interrupting him or losing his attention, and Regulus felt like a proper big brother as he taught Sirius all the important and interesting things he had learnt himself.
In the weeks following Sirius' appearance, the house was often full of people who had been invited to see the new boy. Their mother showed him off proudly to every new visitor and though the adults peered at little boy, exclaiming their congratulations to their parents, they kept their distance from the boy and never pat Sirius on the head or ruffled his hair like they did to Regulus. Despite his young age, Sirius never lost his temper or showed signs of tiredness in these meetings, standing patiently without a smile next to their mother, with only his pale eyes moving, keenly observing the guests who had filled their home. Afterwards, when the heavy winter cloaks had been put away and the adults had drinks in their hands, their mother always ordered Regulus to take Sirius away to play while the adults retreated to the library.
Regulus was eager enough to comply. The two boys would run to Regulus' room and change from their formal, tightly fitted purple trimmed robes to more practical, lighter robes, and then they would sneak past the house-elves in the kitchen, and get into the small pantry. There, behind the crates and away from others' eyes, they would sit and Regulus would tell more stories to Sirius. Sometimes they brought a book or toys from Regulus' room with them, and once Regulus snatched some small apple pies for them when they ran through the kitchen while nobody was watching, house-elves all out of sight.
Pies happened only once, because later Regulus learnt that somebody had seen him taking them and had told their mother about it; probably a house-elf they hadn't noticed in some corner of the kitchen. Regulus was smacked for it and he went to bed that night crying, after swearing repeatedly to their mother that he would never again take anything without permission. You are not to corrupt Sirius, their mother had shrieked while their father had had him over his knee. You are to show him what it is to be an obedient, good son!
Later, years later, Regulus would realize what they had been so afraid of and why, but back then he had only heard 'You should be more like your brother, he is better than you'. Because wasn't Sirius already all they asked for in a son - attentive, silent, and never mischievous? He didn't need Regulus to show him how to be a good boy, he was that naturally. It seemed to him that their parents were only afraid that Regulus' bad traits would corrupt all of that goodness, and make Sirius as bad as Regulus was.
The seeds of bitterness and jealousy were planted in Regulus' mind that day - that maybe Sirius was the one their parents prefered, that maybe all Regulus could do was to imitate his little brother to avoid disappointing their parents.
When Regulus turned nine, the seeds had grown and the bitterness he felt for his little brother leaked through every day. While Sirius had kept to his good ways and their mother had started to take him away from Regulus more and more often for private lessons, Regulus had started to grow apart from both his brother and their parents. In his cries for attention, he stole and broke little things; not very often, but whenever he couldn't handle the bitter emotions inside him. He had temper tantrums that left the elves tutting at him for days, telling him that 'he was a big boy now, the heir of the family, and should be over the outbursts like that by now'.
Regulus wanted to scream at them, to shout at them that he didn't want to be the big boy, he wanted to just be him, and for things to be like they used to be - for his mother to smile at him and not at Sirius, for his mother to take him for special lessons and not Sirius.
Many of the elves felt deep love and sympathy for him, and did their best to keep his outbursts and misbehaviour out of their parents' ears. However, some felt it their duty to report the little heir's actions to the master of the house and his wife. Regulus' toys were taken away, he was often locked in his room and many a night he was sent off the table to think about his behaviour with empty stomach.
But even the punishments felt half hearted and lost their edge over time. Soon he was no longer smacked or slapped for his rudeness, no longer shrieked at, and there was an indifference around his parents about his behaviour that frustrated and discouraged Regulus. He feared that they had given up on him entirely and were turning Sirius into a new heir. He felt angry.
For all his faults in temper, Regulus was also an observant boy. He had noticed how their mother had become fond of her golden ring, the ring which Regulus had first seen the night Sirius had appeared. Their mother enjoyed showing off, wearing new jewelry that matched her carefully planned outfits every week, but that ring was the piece that stayed on her finger every day. It wasn't even the prettiest ring their mother had - it was an odd, roughly smithed piece which was thicker on the top and had no jewels on it. Regulus didn't know where their mother had gotten it from, but he decided to take it away from her.
At least then she couldn't stay indifferent to Regulus, after losing her most valued possession.
In the end, stealing the ring was surprisingly easy. Regulus stayed awake until everyone in the house was asleep, and then he sneaked into their parents' bedroom. He kept quiet as he opened the door and slipped inside, the moonlight illuminating the room for him. He saw the jewelry box sitting next to their parents' bed as he walked to it and took the ring out. It was heavier than he had imagined and as he turned it over in his hands, his fingers found an unexpected edge. He pressed slightly and the ring's thick part flipped open, allowing a small stone to roll into his hand.
He hesitated for only a moment, but guessing that this stone and not the ring itself was what their mother most valued, he decided to change his plans. He put the ring back to the box as it had been, but slipped the stone into his pocket. Satisfied with himself, he turned and almost gave himself away as he was startled by the sight of his little brother standing in the corner of the room.
Sirius was looking straight at him, with his ever so serious, pale eyes, standing fully clothed in the corner. Chills ran through Regulus. It was then that Regulus had to believe what he had always known in the back of his young mind, but never thought of consciously. All the little things pointing to something strange, something otherworldly going on with his brother.
Why hadn't he ever wondered where Sirius slept at night? No bedroom had ever been prepared for the boy. Maybe it was because he didn't need sleep.
Regulus had no answers, only questions he felt afraid to think about for long in the dark, quiet room. Sirius was silent as ever and their parents were still asleep, so Regulus slipped out of the room, with his heart beating in his chest and the tiny stone in his pocket.
The next few days were miserable for Regulus. Their mother didn't notice anything was amiss, and Regulus, shaken from the encounter during the night, had lost some of his fight to rebel. He felt scared, lonely, wandering in the house in between meals and lessons and nights. He wished that his life would make sense again, and that he could go back to those simple days when he had been simply glad to be getting a little brother.
Then one night, as Regulus lay awake in his bed, his door creaked as it was slowly opened.
Regulus didn't turn, frozen as he was in his bed, and could only listen to the footsteps of a child getting closer to his bed. He didn't move as he felt how the boy slipped under the covers and lay down behind him. Regulus' skin broke in cold sweat as he felt little arms coming around him, hugging him.
The touch felt unfamiliar and unnatural, doubly so because it had been a long time since anyone had hugged Regulus. He turned his head, despite his misgivings, and looked at Sirius, whose head was next to his on Regulus' pillow.
"Brother," whispered Sirius, and smiled at him.