A/N: Five times Regulus should have been a better brother, and the one time he got it right. Written for The Five Things Challenge by Cuban Sombrero Gal.

Regulus watches jealously as his older brother and all his older cousins soar around on their brand new brooms, laughing and calling out to each other. He isn't allowed to fly with them. He's only three. He hates being three. He can't do anything.

Regulus pouts, and is about to work himself up into a tantrum, when Sirius swoops down from the air to stop before him.

"Hey Reg! Get on! Let's go for a fly!" Sirius glances longingly at the game the others have begun just once before bending down to place his baby brother on the broom in front of him.

Regulus notices the longing glance and feels guilty, an emotion completely foreign to the three-year-old. "Siwi, awe you suwe you don' wanna pway wid dem?"

Sirius smiles. "I'm sure."

"But...why?" Regulus knows he is grateful to his big brother, but he can't understand why Sirius would be nice to him. No one else is nice to him.

Sirius wraps his arms around his little brother and kicks off from the ground. "What are brothers for?"

Regulus giggles and leans against his brother, feeling completely safe, and very special.

.&.

CRASH!

Scattered pieces of splintered glass shatter the perfect silence of the night. Seven-year-old Regulus freezes in place, hoping the noise didn't alert anyone to his presence. He hopes no one will catch him on his way to the kitchen for a midnight snack.

Cccrrreeeaaakkk… (A/N: How on Earth do you write that noise?)

A door opens from somewhere in the manor. Regulus stumbles clumsily into a shadowy corner. "What was that crash." It isn't a question. It's a statement. An accusation. Though her voice is calm, Regulus knows better. Mum is seething. Someone is going to be punished, and she doesn't care who. He takes a breath, preparing himself to shuffle guiltily into the light.

"Sorry, Mum. It was an accident. I wasn't paying attention." Regulus frowns. That voice…that voice wasn't his. He didn't say anything. But if it wasn't him…

Sirius steps of the shadows to stand in front of their mother.

Regulus can't move, can't breathe, can't look away, as his nine-year-old brother is subjected to Crucio for breaking a vase.

When it's over, Regulus runs to his brother, crying, hating himself for not doing anything.

"Why?" he asks in a trembling voice. "Why did you cover for me?"

Sirius shrugs nonchalantly, ignoring the intense pain lancing down his shoulders. "What are brothers for?"

Regulus smiles weakly, then struggles to help his brother back to bed.

.&.

"Well, well, well, if it isn't Regulus Black. You, my boy, are now at a crossroads. A choice is just waiting to be made. Keep in mind, my boy, I don't offer this choice to just anyone. Pick carefully, now. Slytherin or Gryffindor? Lion or Serpent? Green or Red? Bravery or Cunning? What will it be, my boy?"

Regulus blinks, then blinks again. The hat can talk?

"Of course I can talk," the hat huffs. "I am the SORTING HAT, after all. Now pick your house. And pick wisely."

Well, there was Slytherin, the house his family had been in for generations. And then there was Gryffindor. The house of blood traitors.

Bellatrix, Andromeda, Narcissa. Sirius. His parents. Sirius. Rewind. His parents. They'll kill him if he isn't in Slytherin.

That makes his decision. He rather likes being alive, thank you very much.

Slytherin, he thinks. Please, I choose Slytherin.

"Slytherin, eh? The house of the cunning, the sly, the ambitious. Well, if you're sure…Wait! There's something you should know. As a rule, I never let students choose their own house. Too young, you know. Actually, I suppose you don't know...But I made an exception for you. Your brother specifically asked me to give you this choice. Seemed to think you'd make the right decision." The hat pauses thoughtfully, then screams, "SLYTHERIN!"

Regulus walks to the Slytherin table in a daze, toward Bellatrix, Andromeda, Narcissa, his parents, one word running through his mind. Sirius. Sirius. Sirius.

He chances a glance at his brother, but Sirius has his back turned to him.

After dinner, Sirius is surprised to see his little brother appear in front of him.

"Why?" Regulus begs. "Why did you give me that choice?"

Sirius laughs coldly. "What are brothers for?"

Regulus stares helplessly at his brother's retreating back, then squares his shoulders and looks around for a prefect to guide him to the Slytherin common room.

.&.

"GET OUT OF THE HOUSE, YOU UNGRATEFUL BRAT!" His mother's piercing screams reverberate unpleasantly around the house, all the way to Regulus's room, where he has holed himself up to avoid the fight.

"YOU ARE NO SON OF OURS. OUT! OUT! OUT!" His father's thundering shouts add to the mix. Regulus swears he can feel his ears bleeding.

This is it. Sirius has finally been disowned. Everyone knew it was going to happen someday. But where would he go? He is only thirteen, for fuck's sake. He couldn't very well live on the fucking street. But maybe...maybe Regulus could hide him in his room! And get Kreacher to bring extra food! And…

His thoughts are interrupted by a soft knock on the door. "Reg? Reg, can I come in?" Sirius hasn't called him Reg in years.

"It's open." His door will always be open for his big brother. Always.

"Reg, I'm leaving. The bitches finally kicked me out. Come with me! We can go live with the Potters. They won't mind! Come with me! Don't let them poison your mind with all this pureblood shit. Please, Reg. Let me save you. Save yourself!"

As much as Regulus wants to follow his brother, he knows he can't. He isn't strong enough to defy their parents.

"I—I can't. I just—I can't. I'm sorry."

Sirius's eyes flash with disappointment, then fill with sadness. Mixed in with the sadness is understanding. The understanding is the worst of all, Regulus thinks. Sirius can't understand. He isn't a coward. He's the strongest, bravest person Regulus knows. He isn't a coward. Regulus is. Regulus is the fucking coward. Not Sirius. Never Sirius.

Sirius pulls him in for a brief hug, their first hug, ever, then turns away sadly. "Goodbye, then."

"Wait! Siri! Why?" Regulus is close to tears. "Why did you ask me to come with you?"

Sirius reaches down sadly to ruffle his hair. "What are brothers for?"

Regulus clings to the doorframe as Sirius silently makes his way down the stairs and out of his life.

.&.

A cold laugh.

That's all it takes to convince Regulus not to turn the corner. Bellatrix is there, and he knows she's doing something he'd rather not see.

A warm laugh. "What's the matter, Bella? Lost your touch? Old age catching up with you I see."

Fuck.

It's Sirius.

He hasn't heard his voice in three years. But Regulus would always know that laugh. Always.

A series of thuds. A body thrown against the wall. Over and over.

Regulus leans heavily against the wall and squeezes his eyes together.

The way he sees it, he has three options. A, he can intervene, save his big brother, and face the wrath of Bellatrix Black himself. B, he can turn around and go back the way he came, pretending nothing had happened. Or C, he can stand here, vacillating between the first two options.

He is just about to choose option C when a third voice sounds in his ears. "Paddy? Padfoot? Sirius? Sirius!" The new voice gasps, then calls out a curse, one Regulus has never heard before.

A moan. A threat. A menacing growl.

Bellatrix stalks around the corner muttering angrily to herself. Something about revenge, and "fucking blood traitors". She is oblivious to her cousin clutching the wall. Her footsteps soon fade into the distance, and Regulus finally gains the courage to peek around the corner.

James Potter.

James fucking Potter saved his brother. His brother.

"Hey, mate, you alright?"

NO! Regulus wants to scream. Does he fucking look alright?

"Yeah," Sirius grunts. Potter bends down to gently help his injured best friend into a standing position. Regulus has to admit that maybe, just maybe, James fucking Potter isn't completely stupid. Maybe he's pretending nothing happened just to maintain Sirius's pride. Maybe.

"Um…thanks, mate." Sirius sounds awkward. "Why…"

James smiles warmly at his best friend. "What are brothers for?"

Regulus has never cried so hard in his life.

.&.

Regulus lets out a bark of laughter as the memories flood his mind. He's a horrible brother. He's always known it. A horrible brother. The fucking worst brother, ever. He could probably win a medal for it. The thought makes him snort. Sirius has helped him so many times, so many ways. But what has he done in return? Nothing. Not. A. Fucking. Thing.

He glares at the basin in front of him, as though it was all the basin's fault.

What are brothers for?

What, indeed. But Regulus thinks he knows.

"Now listen to me, Kreacher. Ignore everything I say after this. I want you to keep handing me cups of this liquid. No matter what I say. When the basin is empty, take the necklace inside and go home. Get rid of the necklace. I don't care how. Can you do that for me?" He knows the voice must be his, but he can't feel his mouth moving to form the words. His brain barely processes Kreacher nodding his small head. "Thank you, Kreacher. Thank you so much. For everything." The house elf looks at his master, startled. Was he just thanked? Was he supposed to say something? But Regulus doesn't notice the creature's dilemma.

This is it. This is the end. He's made his decision. There's no going back.

But that's okay. Because Regulus is willing to give up his life for his brother. Fuck, he'd die all over again, again and again, if it meant his big brother could live just one more day.

And that's what brothers are for.

A/N: This story was written partly because the challenge was begging to be put into words, partly because the Sirius/Regulus dynamic was intriguing, but mostly because I needed to come up with a reason for brothers to exist. I have three. x_x