Sometime later, both the Potter children had composed themselves and sank onto a couch opposite Hermione. "I have a family." Harry whispered, still looking quite shell-shocked. "They're alive. But how? Christina, how did you survive?"

"I don't know." Christina muttered.

"How did no one at Hogwarts recognize you?"

"I don't know."

"I have a theory on that." Hermione piped up.

"Of course you do."

"Well, first of all, everyone thought you were dead. But Christina's last name was Evans on the school roster. But people weren't looking for a Christina Evans, they were looking for Christina Potter. But you should have had a visit from Professor McGonagall, if they truly thought you were muggleborn, and she should have recognized you then. What happened?"

Christina shook her head. "I never saw Professor McGonagall over summer. She was ill the week muggleborn home visits were supposed to happen, so I met Professor Vector instead."

"Hermione's eyes widened. "That makes so much sense. Professor Vector doesn't get out much, so she wouldn't necessarily recognize your mum. But why didn't your mum tell you about your family? Why didn't she say anything about your name being incorrect on the school's roster? Was she going by Evans too?"

Christina shrugged. "I don't know. Evans was the only name she remembered."

"But the both of you are Potters." said Harry. "You shouldn't ever have been Evans."

Christina winced. "My mum's an amnesiac. She doesn't hardly remember anything before 1981, only little bits and pieces. She doesn't remember you or Voldemort or being married, I guess, since she only remembered someone calling her Evans. She only remembered Hogwarts when I started coming here."

"That explains so much." Hermione whispered. "It explains why she never corrected the last name, never tried to contact Harry, why you had no idea you even had a brother.

Harry was staring at her. "You don't know anything." He muttered. The blood had drained from his face and his hands were shaking. "I mean, you don't know anything about our family. I don't know much, but I know more than you do." He ran upstairs to his dormitory and came back with a photo album. "Hagrid gave me this a few years ago. It's got as many pictures of our parents as he could find. Here." He flipped to the picture of their parents on their wedding day. "You should take a look."

"That's really Mum and Dad." Christina reached out and caressed the edge of the photo with two fingers, just like she'd done with the photo of her mother in the yearbook. "Merlin, I have a dad. He looks just like you."

"That's what everyone says. That I look like Dad, but I've got Mum's eyes." He squinted at Christina. "You look like Mum."

Christina nodded. "Everyone says that." She took another look at the picture. "Who's that?" she asked, pointing at their best man, but even as she said it she knew who it was.

Sirius Black." Harry ground out.

"He was—"

"Friends with Dad, yes. He betrayed them. Now we think he's coming back to finish me off."

"Piece of scum." Christina muttered. "That must be why you look so angry all the time." She glared at Black's portrait, but curiosity got the better of her and she continued flipping pages. There were lots of pictures of her parents and several with baby Harry, but only one with all four of the Potters. Lily was holding one-week-old Christina, who was no bigger than a loaf of bread, while Harry looked like he was trying to escape his father's grip. The picture highlighted just how close in age the Potter children were. James and Lily, at the tender age of 21, had been wrangling two babies before they died.

"This picture has the date as the 19th, and Voldemort came for them on the 31st." Harry said.

"You need to start at the beginning and tell me everything you know." Christina said. "Please. Maybe we can piece together what happened to me and Mum."

Harry nodded, but didn't make a move. Finally he muttered, "Where's Ron? I want Ron. For moral support."

Hermione stiffened.

"Hermione, would you just admit that Crookshanks maybe caused some problems and probably did eat Scabbers?"

"Are we still arguing about this?" Christina asked. "Didn't Crookshanks eat Scabbers a couple months ago?"

"We all knew Scabbers was on his way out anyway." Hermione said, ignoring Christina. "Frankly, I think Ronald should be happy that Scabbers crawled away and found a private space to die quietly."

Harry rolled his eyes. "Would you please admit that there's a chance Crookshanks ate Scabbers?"

"Fine. Because of the unique circumstances in this situation, I will admit that there is a non-zero chance that Crookshanks ate Scabbers."

"Thank you. I'll go find Ron." He scrambled out of the portrait hole, leaving Christina alone with Hermione.

"Now that I think about it, you really do look like him." Hermione mused. "Not when it comes to hair color or eye color, obviously. It's kind of interesting how genetics worked out. I think you two have the same smile."

"How did you figure it out? I mean, how did you look at the pictures and figure it out so quickly, when Harry and I were at each other's throats?"

Hermione sighed. "First of all, I read, which is something your brother could try once in a while. I read about your family in The Rise and Fall of the Dark Arts, in which the author speculates what happened to you and your mum. Secondly, I'm a touch more observant than Harry and Ron. If I wasn't, we'd all be dead by now."

Christina nodded. Having Harry as a brother meant that she would probably be spending more time with Ron and Hermione, whose favorite hobby appeared to arguing with each other. It was a wonder Harry hadn't completely lost his mind yet.

"You've got a what now?" Ron's voice echoed across the common room as he and Harry came through the portrait hole.

"A sister." Harry pointed to her. "I know it doesn't make a lot of sense. We have to show you the photos."

"Bloody hell, Harry, she doesn't even look like you. Are you absolutely sure?"

"Pretty sure." Harry sat down on the couch and showed Ron all the photographs they'd amassed.

"Blimey." Ron muttered. "I suppose congratulations are in order, but mate, little sisters are the worst."

Harry picked up the old yearbook and gave Ron a brief rundown of what they'd found out. By the end of it, Ron was gaping like a fish.

"Bloody hell. Your mum's an amnesiac? And your sister doesn't know anything, because your mum's an amnesiac. She doesn't even know why you-know-who went after your parents."

"I know that much." Christina muttered, but she was cut off by Hermione.

"Ron's right, we need to fill Christina in. There's a lot she doesn't know. Harry, why don't you tell her about yourself?"

So Harry started from what he knew, about Voldemort targeting the Potters and Sirius becoming their secret-keeper. How James's body had been found, but only a scorch mark on the carpet where Lily had been standing. How Voldemort had been vanquished and Harry became the Boy Who Lived. How Sirius Black had sold them out, then killed Peter Pettigrew and gone to Azkaban. He told her about Aunt Petunia and Uncle Vernon and Dudley, but something in the way her large hazel eyes stared up at him made him hold back the worst details, like the cupboard under the stairs and how he'd learned not to stand within arm's reach of Uncle Vernon.

"We both grew up in the muggle world, despite not actually being muggleborn." Christina interrupted. "Funny how that happened. What was Dad's blood status?"

"Pureblood." Harry supplied. "And Mum's muggleborn, making us halfbloods."

"And we're famous, because you're the Boy Who Lived?"

Harry made a face. "Trust me, you don't want to be famous. People used to whisper in the hallways when they saw me go by. Everyone was pointing me out to their friends. Why, you should have seen the way Colin Creevey treated me last year."

"Well, I think I'm going to like it."

"No you won't."

"Harry, I was a nobody. I didn't know who my own family was. Mum feels like a nobody too. We didn't know who we were for my entire life."

Harry snorted. "I was a nobody too. But being somebody was awful too. The only good thing about existence is the people you meet who make life worth it."

"You're getting rather existential here, Harry." Ron muttered.

Christina rolled her eyes. "Of course I know that the people you meet are the ones who make life worth it. But still, it feels good to know who I come from. You know? It satisfies that itch deep in my soul."

Harry just stared at her. "My soul doesn't itch. I don't find myself having a lot of deep desires."

Hermione was clearly trying not to laugh. "Harry why don't you get on with your story? Tell her about what we did at Hogwarts."

So Harry launched into the tale of his Hogwarts years, telling her about everything from joining the quidditch team to the mirror of erased to Draco Malfoy. He told her about Norbert and the sorcerer's stone and Professor Quirrell. Then there was the time the Weasleys had broken him out of the Dursley's house, and the time he and Ron had flown the car to school.

"Wait, wait, wait." Christina interrupted him. "Why on earth did you fly the car to school?"

"We'd missed the train. Thanks to Dobby the house elf, who—"

"But why would you do that in response to missing the train?" Christina asked. "Why not wait for an adult? Or contact Professor McGonagall?"

"We didn't think of it at the time." Ron said.

Christina gave both of them a scathing look that clearly said, "What on earth is wrong with you?"

Harry kept talking, telling her about the chamber of secrets and how he'd suspected Malfoy, which had lead them to make the polyjuice potion. Then people had starting suspecting him as being their heir, and then Hermione had been petrified. He told her how they tracked down Moaning Myrtle, then found the chamber and rescued Ginny.

"I've never met Moaning Myrtle." Christina mused. "I avoided that bathroom because an older student told me horror stories about it."

"Keep it that way." Harry grunted. "Trust me, you wouldn't like Myrtle."

"So you've seen all the weird stuff at Hogwarts. I've just been reading books and playing pick-up quidditch and fainting every time I see a dementor."

"What position do you play in pick-up quidditch?" Harry asked.

"I've tried chaser and had fun with it. I tried beater once, but Andy Sommers—do you know him? Andy Sommers told me I wasn't strong enough to hit the bludgers. My left side's a little weaker than my right."

"You know why you faint around dementors, though, right?" Hermione asked, clearly scandalized that Harry had latched on to the wrong part of Christina's experiences at Hogwarts.

Christina nodded. "Messed-up past. Professor Lupin told me. All I hear is Mum screaming. Something about how she had to go back."

Harry looked at her, his expression unreadable. Finally he said, "Start at the beginning. Tell me everything you've been doing. Maybe we can piece together what happened to Mum."

"The earliest Mum can remember is waking up in a hospital in London on November 2nd, 1981. She got a job and a flat and we've lived there ever since. Mum works as a secretary and I went to primary school in London. Last summer I got my Hogwarts letter and that's when weird things started happening, like Mum saying she thinks she went here too. I was doing Sienna Markey's Muggle Studies project where she was interviewing muggleborns, and I told her about Mum thinking she'd gone here. Sienna told me to see if Mum was in an old yearbook, so I took one and found her picture. It's the strangest thing," she laughed a little, "Sienna told me that the woman I found in the yearbook looked like Harry Potter's mother, and to tread carefully. Neither of us figured it out until Hermione put two and two together."

"Yeah, well, Hermione's bloody brilliant." Ron muttered. "If anyone would figure it out, she could."

"Why thank you, Ron." said Hermione, unable to hide the surprise in her voice. "That's very kind of you."

"Always the tone of surprise." Ron said.

"So what do we do now?" Harry asked. "Write a letter to Mum and try to explain everything?"

"No." Hermione set down Hagrid's photo album, nostrils flaring. "We tell an adult."