Regulus Black had gone to the library rather than staying in the Slytherin Common Room. Severus, no matter how much he tried, couldn't quite stir up a crowd the way Bella could. And Narcissa just sat there ignoring him, blood relative or not. He tried to participate--really, he did--but Severus's speeches were always about using powers that Regulus wasn't even sure he had. Bella's had been about wizarding pride and blood ties. She'd left school the year before he came, but he'd heard her speeches at home, and the older Slytherins--when Severus wasn't listening--often said that they missed hearing her.

So Regulus had wandered down to the library and pulled out an old book about the feud between Merlin and Morgana, with a lot of speculation about who Niniane might have been, which Regulus liked a lot. He was sure that if he dug far enough back, he would find out that the Black family was descended from Merlin and Niniane. He hadn't shared this with anyone yet. He wanted it to be a great surprise.

Thud. Thud, thwicker, thud, thud...

Crash.

"Mr. Black!" Madam Pince scolded.

Regulus tensed in his seat, then he heard Sirius say, "Sorry. I've got it."

There was the sound of something whistling through the air, then another series of thuds as the books he'd knocked off the shelves slammed back into place.

Regulus took a deep breath and picked up his book, holding it like a shield in case Sirius was still angry with him, and looked around the end of the shelves.

"Sirius?"

Sirius turned on him, his eyes deep and dark-seeming, even though they were light-colored. "What are you doing here, Reg?"

"Reading."

"Right." Sirius jutted his chin at the book in Regulus's hands. "What've you got? History of Magic?"

"No. It's just for me."

"Mind if I join you?"

"Why? Are you having another fight with your Gryffindor friends? Thought you'd slum with your blood a bit?"

Sirius looked at him for a long time, then flicked his hands in a dismissive way. "Forget it. Forget I said anything. Forget I was here."

He stormed out of the library.

Regulus put his book back on the shelf, somewhat regretfully, and followed him out.

As he'd expected, Sirius hadn't headed back to Gryffindor. He was sitting on the staircase in the Entrance Hall, staring at the door, which had shut for the night.

Regulus sat down beside him. "Severus said all Pure-bloods are brothers. He said all Slytherins are brothers as well, so I'm his brother twice and yours only once."

"Does he, now?"

"Mm-hmm."

"He's a git."

"I told him I already had a brother, and didn't especially want another one."

Sirius gave him a guarded look, then, very slowly, smiled. He had a way of smiling that made everyone else around him smile, and Regulus couldn't help giving it back.

Sirius grabbed him around the neck and mussed his hair roughly with an extended knuckle. "I love you, too," he said. "You are an idiot, though. Snivellus--"

"--Severus--"

"--whoever--is about as interested in your welfare as..."

"As what?"

Sirius shook his head. "Never mind."

"You think he's just my friend to annoy you?"

Sirius didn't answer.

"I think so, too."

"You do?"

"Yes. But I think we should all be sticking together now."

"We, who?"

"You know who. The old families. And it's not right the way you're nasty to Severus, so I'm nice to him to make up for it. If you want me to stop, you stop."

Sirius frowned deeply. He couldn't very well say anything.

Except, of course, that he did. "Regulus, you're too worried about all this blood purity nonsense."

"It's not nonsense. Have you seen what they bring in?"

"I've seen all the things Bella blames them for. That's not the same thing."

"Right. Andromeda would have run off and eloped and had that freakish baby of hers if there were no Muggle-borns..."

"Don't you dare start on Andromeda and Ted and Nymphadora--"

"And we wouldn't be constantly on the edge of being revealed to the Muggle world--"

"Why is that such a horrible thing?"

"And you and I wouldn't be fighting like this..."

"You're the one who's being stubborn about being wrong!"

Regulus sighed. Sirius was determined to rebel against everything Mum said. "We should stop now," he said. "I don't want to fight anymore."

"Neither do I."

"Good then." Regulus stood up. "It's my curfew. I have to get back."

Sirius didn't say goodnight. When Regulus reached the stairs that headed down to Slytherin, he looked back, and saw his brother still on the stairs, looking at the floor now, not moving.