A/N: By request, little Sirius and Regulus, aged 10 and 7 :)

April 1970.

Sirius held his little brother's hand tightly as he pulled him along the narrow alleyway that was Knockturn Alley. Something about this place made his belly hurt. Regulus, however, did not seem to notice it. The seven-year-old walked with his head tilted back, the gray of the sky reflected in his large gray eyes.

"What's that, Siri?"

"What?" Sirius stopped momentarily.

"That, up there." Regulus raised his free hand, drew a line in the air that followed the ragged remains of a contrail which an airplane had scribbled across a break in the clouds on its way to Heathrow Airport.

"Birds?"

"No," giggled Regulus. "The white stuff that's coming from the airplane's bottom."

"Plane poo," Sirius said matter-of-factly. He lowered his voice slightly as he always did when they talked about muggle things within earshot of one of their parents.

Regulus screwed up his face. "But it's white!" His voice was like a bell.

"Yes. Plane poo is white. Come now," Sirius said, tugging on the child's hand. He had to stand on his tiptoes to see his mother. She had not noticed that her sons were not behind her anymore and had moved across the busy alley to inspect an unlit shop window. Sirius stopped behind her, Regulus' hand tightly enclosed in his. He tried to see what she was looking at but saw nothing but his reflection staring back. Some of the shop windows in Knockturn Alley concealed themselves to passers-by who were not looking for the particular Dark Arts objects on display.

"Wait outside," his mother said without turning, her eyes flashing slightly as they traveled to Sirius' and Regulus' reflection.

"How long?" Sirius knew his annoyance was showing. He hated how she left them waiting forever sometimes, so long that Reg began to ask whether she had forgotten about them.

His mother flashed him a dark look. "Watch your brother."

"Yes, Mother," Sirius drawled. Regulus echoed his words innocently.

She disappeared into the store, a bell ringing as the black-painted door swung open.

Regulus sighed exasperatedly. "Siri, I'm bored!"

"I know. Me too."

"Can we go to the Quidditch Store?"

Sirius sucked at the inside of his teeth, glancing at the door to the store which had closed behind his mother. If he knew that she was going to stay in there for more than five minutes - but you never knew. "Later, maybe."

Regulus sighed again. He leaned back, trusting Sirius to hold him up by his hand.

"Stand properly," Sirius said, frowning. "You're not a baby, are you?"

"No," Regulus responded with a grin, revealing the gap between his front teeth. He did not stand upright, however, instead, he let himself fall back even more, swinging from side to side slightly as though Sirius' arm was a rope. If Sirius were to let go of his hand, he would be falling onto his back.

Sirius hauled his little brother to his feet. "Stop it," he said forcefully. He was not in the mood to serve as a climbing frame for the child.

Regulus stumbled forward. "You're boring."

Sirius rolled his eyes. "And you're annoying," he said.

"I'm not!"

"Mother's gonna be back in just a moment and you don't want her to catch you playing around. Now stand still."

Regulus dropped to the ground, eliciting a grunt from Sirius as the older boy's arm had to take the full weight of the child.

"Get up." Sirius' voice from above, a command accompanied with a harsh tug on his arm.

Regulus shook his head. He sucked at the loose tooth he'd had for a few days now on the bottom, pushed at it with the tip of his tongue, wiggling it back and forth. He tilted his head back, using his finger to hold the tooth at an angle to show it to his big brother. "Siri, look!"

Sirius tugged at his arm again, causing the boy to lose his balance slightly, his fingers slipping on his tooth. Sharp pain in his gum followed as he was forced up and onto his feet, then the taste of blood in his mouth. "Ouch!"

"Stop complaining," Sirius barked at him, oblivious to what had just happened.

Regulus gazed at his hand. The tip of his right forefinger was bloody. The blood was from his mouth, where his tooth had been. It was gone now. Tears shot into his eyes as he looked up at his big brother. He lifted his hand so Sirius could see the blood.

Instantly, the annoyance in Sirius' face disappeared and replaced by concern. He bent down to inspect the finger more closely. He wiped the blood off, realizing that there was no cut, it wasn't the finger which was bleeding.

"It's gone," Regulus whimpered.

"What's gone?"

"My tooth."

This was when Sirius spotted the new gap on the bottom of his little brother's teeth. "It's no big deal," he said, relieved that Regulus wasn't hurt - at least not for real.

"But it's gone!"

"It'll grow back. See, there's already a tiny white nib growing in its spot."

"Nno," the child's breath was hitching. Tiny tears were clustering in the corners of his eyes. "I have nothing f-for the tooth fairy."

"Oh. You don't have it?"

A sob broke free from the little boy's chest as he shook his head.

Sirius frowned. He crouched down, his eyes scanning the ground. It was very well possible that the tooth had fallen into the gaps between the cobbles if Regulus had pulled it out accidentally. If he hadn't, there was little point in searching the cobbled area. People were pushing by, their boots loud on the cobblestone street, their long black coats brushing across it. "Do you know if, perhaps, you swallowed it?"

Regulus looked horrified.

Sirius sighed. "Then you probably didn't." He picked up a white pebble stone of about the size of his fingernail and inspected it before flashing his brother a wide grin. "Oh, look, is that it?"

His brother looked indignant at the suggestion. "No! It was tooth-shaped!"

"It totally is tooth-shaped," Sirius protested weakly, but at the expression on Regulus' face, he dropped the pebble.

Scanning the area one last time, Sirius sighed as he got to his feet. He wrapped his arms around the crying child. "It's okay," he said gently into his brother's ear, "the tooth fairy won't mind. She can see that you have a tooth missing."

The child shook his head, pushing Sirius away. "She c-can't! You said I have to k-keep it under my pillow -"

"Yeah, but she can find it if we leave her a note."

Anger, flashing up in Regulus' eyes. It was of the helplessly outraged kind, similar to the feeling of being talked down to. "No, she can't! It's gone! And it's your fault!"

"It's not my fault you can't keep track of your own stupid tooth," Sirius responded, annoyed now. "Stop being a baby about it."

"I'm not a baby," Regulus yelled, shoving at his brother's arms.

Sirius rolled his eyes. "You keep saying that. Only babies say that they're not babies." He crossed his arms, leaned against the tarnished shop window with the intention of ignoring his little brother's antics. "I can't wait to go to Hogwarts," he muttered to himself.

Regulus froze mid-tantrum. Sirius looked away stubbornly, knowing that his brother had heard that.

The bell rang again and their mother exited the shop, the sound of her heels clacking on the hardwood steps causing Sirius to take a quick step towards his little brother again, find his hand.

"Let's go, boys," their mother said as she brushed past them, barely glancing at her sons.

Their mother was trying on dresses at Twilfitt and Tatting's, turning in front of the round, gilded mirror across the room, the expression in her face emotionless. "It is still too short," she said coldly.

A sales assistant knelt next to her, nervously flicking her wand in a complicated manner at the billowing hem of the emerald-green satin dress. Sirius knew how hard it was to please his mother, she was like the desert sun, her pale face an unforgiving sneer from which there was no shelter.

Sirius felt Regulus move next to him and looked down, saw the child rubbing his hand over his eyes, still sniffling. Sirius sighed softly. It had been nearly twenty minutes and Regulus was still upset over the tooth he'd lost. Sirius was starting to worry a bit. His mother mustn't see Regulus' tears, they were bound to annoy her.

"Honestly, Reggie, it's not that big of a deal," Sirius whispered as he gently pushed his brother to stand behind a wooden clothing rack where his mother could not see him.

Regulus turned his face away, his floppy hair falling into his face and hiding his eyes.

Sirius hated it when Regulus was upset. He rubbed a hand over his face, glancing at his mother, then at the front door. Maybe, if he went back to find the tooth, it might still be there somewhere. Maybe he had overlooked it.

"Reggie," he said in a strained whisper, "what if I go back to find the tooth, hmm? Will you stop crying then?"

Two gray eyes, red-rimmed, blinking up at him. "You'll find it?"

"I'll do my best. Can you distract Mother in case she starts looking for me? Just tell her I went upstairs to look at the Hogwarts school uniforms if she asks where I am."

Regulus snuffled. "Okay," he said softly. Despite being only seven years of age, Regulus knew how to lie and he could do it well. Sirius had taught him how.

Sirius waited for a new customer to enter the store. He squeezed past an elderly man with frizzy white hair who held the door open only a second too long while pocketing his wand and commenting on how it was coming down in buckets outside. Unseen, the ten-year-old boy stepped into the rain, quickly glancing around before hurrying down Diagon Alley and turning into Knockturn Alley. The twisted alleyway wasn't as crowded anymore, the rain had driven most shoppers into the stores.

It didn't take him two minutes to reach the spot where Reg and he had been waiting earlier. The obscure shop window was barred now. Knockturn Alley was even eerier like this, all empty and deadly silent aside from the sound of the rain pouring onto dirty roofs and drumming against closed windows.

Sirius knelt on the cobbled alley, the hem of his coat getting wet as it brushed across the ground. He checked every single crack between the cobblestones, even felt around the puddle that was forming on the uneven ground, reflecting the light from the dim street lamp above. Nothing. He grew more nervous by the minute. His mother would notice his absence soon.

It didn't matter how hard Sirius looked. The tooth was so small and light it was likely it had been washed away by the rain. He rose again, desperately looking the ground over once more, looking for that tooth which only an hour ago had been part of his little brother, had belonged to Reg like his eyes, fingers or toes, and now it was gone. Raising his hand to his mouth, Sirius tested the stability of his own teeth. He couldn't pull any out, however, they were permanent teeth that had come to stay.

The white pebble was still there, however, the same one which he had half-jokingly offered Regulus as a replacement. He picked it up, turned it between his thumb and forefinger. With a bit of imagination, it did look like a tooth. He slipped it into his pocket. Then he forced himself to turn and head back to Twilfitt and Tatting's, raindrops pattering across his skin and hair.

"Where have you been?" His mother's sharp voice, the reflection of her eyes flickering into his direction for a second. She only noticed things she didn't like, Sirius had learned that about her long ago. Things like smiles, his hair growing past his ears, or her children not following her orders to the letter.

Sirius peered at Regulus who was standing next to their mother. His little brother looked tiny next to her, like a baby chick next to a fully-grown eagle. It was like a single stroke of her wings could blow the child away. "I was upstairs," Sirius said, hoping that she wouldn't smell the rain still clinging to his clothes. "I wanted to try on the Hogwarts uniforms."

"You're supposed to watch your brother, not play around," his mother said harshly yet she was barely sparing him a glance as she spoke.

Sirius nodded quickly, stepping closer and taking Regulus' hand into his, his little brother's fingers warm compared to his. "I'm sorry, Mother."

"Do not let it happen again." She turned back to the sales assistant who was folding the midnight-blue satin dress Walburga Black had finally settled for and before storing it in a shopping bag. And then, with her back turned towards her sons, she added, "the time for Hogwarts will come soon enough."

Sirius felt Regulus' fingers tighten around his. He looked down, smiled at his little brother.

"Did you find it?" Regulus didn't voice it like a question, he was so certain that Sirius must have found it because Sirius could do anything.

"Yeah," Sirius lied.

"Can I see it?"

Sirius' fingers closed around the pebble in his pocket just to reassure himself that it was still there. "When we get home I'll put it under your pillow."

"But can I at least see it?"

Sirius hesitated before pulling the pebble out, keeping most of it hidden in his palm so his little brother only saw that there was something small and white in Sirius' hand.

When the boy reached out to touch it Sirius withdrew his hand and slipped the pebble back into his pocket. "No. You'll drop it and lose it again."

Regulus' eyebrows creased a little bit as though he contemplated pouting but then his forehead went smooth again. "Thanks," he said softly, leaning against Sirius, letting his big brother take some of his weight like a cat rubbing against legs.

Sirius placed a hand on the child's shoulder to steady him, tickling the back of his neck with his other hand which earned him a giggle from his little brother.

The sound of Reg's footsteps from the corridor outside his bedroom made Sirius listen up. The door opened just far enough to allow the small child to enter Sirius' bedroom. Sirius sat up, rubbing his eyes. He closed the book he had been looking at, an illustrated edition of Hogwarts: A History.

Regulus jumped onto his bed. He was in his pajamas already.

"Did you brush your teeth?" Sirius asked.

A quick nod. "Do you have my tooth?"

"Yeah, I have it. You have to bring your pillow though or the tooth fairy won't know it's yours. She'll think it's mine if we put it under my pillow."

That made sense to Regulus and he slipped out of the bed once more to retrieve his pillow.

Sirius jumped up as well as soon as the child had left the room. His robes, which were still drying, were hanging on the wall next to his closet. He palmed his pockets and found what he had been looking for - the white pebble stone and a shining new galleon which he had later stolen from his mother's purse.

Regulus returned, carrying a huge, fluffy pillow. He climbed into Sirius' bed, placing the pillow next to Sirius'.

Sirius switched off the light, then lifted the covers, patted the spot next to himself. The child scurried over. Sirius showed him the pebble again, careful that Regulus caught only a glimpse of it. In the darkness of the room, it did look like a real tooth.

"I'm putting it under your pillow. The tooth fairy will come when you're asleep." Sirius lifted his brother's pillow slightly, placed the pebble in the middle before covering it up gently.

Regulus watched this curiously. Then, suddenly, a deeply thoughtful expression manifested on his face. "Have you ever seen her?"

"No," Sirius answered honestly.

"Then how do you know she's real?"

Sirius froze. He had never thought that Reg might doubt her existence. "Doesn't the galleon under your pillow prove to you that she's real?"

Regulus shrugged. "Anyone could have put that there. Maybe Kreacher is the tooth fairy." He giggled at the thought.

Sirius frowned. "Kreacher isn't a fairy. He's an elf."

"Yeah, but what if!" For some reason, Regulus thought that the idea of Kreacher as the tooth fairy was hilarious.

Sirius didn't share that sentiment. Kreacher had done nothing to deserve the title of the tooth fairy and he felt a jolt of jealousy at the mere suggestion. "He's not. He doesn't even know you lost a tooth. Only the tooth fairy knows."

Two gray eyes, blinking up at him. "And you."

"What?"

"Only you and the tooth fairy know."

"Mhm. Yeah," Sirius said in an indifferent tone as though this was a mere coincidence. He nestled his little brother's warm head under his chin, thinking of the galleon which he had hidden in between the pages of Hogwarts: A History right next to him. As soon as the child was asleep, he would switch the tooth for the galleon. All he had to do was stay awake for a little longer than Reg which, honestly, wasn't hard. He imagined how Reg would find the coin in the morning and Sirius would pretend to be asleep so Reg could shake him awake and tell him that she was here, Siri, look, look what I got! Reg's voice, it was like bells chiming when he got excited. And Sirius, he'd play along, marvel at the shiny golden coin with an expression of wonder, and they would look for the tooth and find it gone.

Regulus played with the edge of his pillow for another moment, contemplating the identity of the tooth fairy. Then he yawned and stretched, his black curls tickling the side of Sirius' face. "Siri?" he asked, his voice slightly muffled.

"Hmm?"

"Love you."

Sirius could feel his brother's breathing evening out against his neck. "Love you too," he whispered back.