John finished typing up a blog of his and Sherlock's latest case and closed his laptop with a sigh. Nothing else to do for the rest of the day, he went to the kitchen and made himself a cup of tea. Sherlock was at Saint Bart's doing some experiments that couldn't be carried out at the flat, so John was alone with nothing to do. He could go out, but he didn't really feel up to it. He walked back into the living room. There were binders of old cases that Sherlock had invited John to flip through anytime he wanted. John hadn't taken up his offer yet, but seeing as he had nothing else to do that day, he figured he might as well.
He pulled a binder off the shelf and flipped through it. It was filled with photos of crime scenes, gorey photos of murder victims, notes from experiments Sherlock had done and occasional bits of information about suspects scrawled down in Sherlock's messy handwriting. John put the binder back on the shelf and picked up another one, filled with more of the same.
After skimming through several of the binders, John noticed a small photo album pushed to the back of the bookcase. Curious, he pulled the album off the shelf and opened it. There was a photo on the first page of a little boy who greatly resembled Mycroft and a woman in a hospital, holding an infant in her arms. Underneath the photo, "Baby Charlotte" was written in neat, cursive handwriting.
"Hm," said John, looking at the photo. Who was Charlotte? John didn't remember Sherlock mentioning anything about having a sister. A cousin, maybe? John turned the page and saw several more photos labelled "Mycroft and Charlotte", though they seemed to be out of chronological order; in some photos, they looked like they were in primary school, others they were just toddlers.
On the next page, there was a photo of Mycroft and Sherlock; Mycroft looked about seventeen and Sherlock, maybe fourteen. Mycroft wore jeans and a t-shirt and Sherlock was wearing black jeans with converse and an oversized Led Zepplin t-shirt. His dark, curly hair ran wild as it always does. He was very thin, as he is now, but John noticed his hips looked much wider and the shirt was tight across the upper portion of his chest. Under the photo in the same neat cursive handwriting were the words "Mycroft and Charlotte".
John stared at the writing for a few moments and then studied Charlotte's face carefully. She was almost identical to Sherlock. Same nose, same eyes, same hair, same cheekbones…just slightly softer, more feminine.
He turned the page and saw photos of a little girl around three or four with Sherlock's messy brown curls. The same blue-ish-green eyes his behind dark brown bangs and she wore a pretty white dress.
"Charlotte."
Every photo had Charlotte written under it. There were no photos labelled "Sherlock."
The door to the flat opened and Sherlock stepped into the flat. "You'll never believe what - " He stopped in his tracks, spotting the photo album in John's lap. "What are you doing with that?!" he shrieked.
"You…you said I could look through your albums…" said John, "and I - "
"Not that one," Sherlock said, ripping the album from John's hands and slamming it shut.
John studied Sherlock's face carefully.
"Who's Charlotte?" he asked softly.
"No one," replied Sherlock. "She's no one."
"What do you mean, 'no one'?"
"I mean, no one," insisted Sherlock. John held Sherlock's gaze, making it clear that he had no intention of letting it go. Sherlock sighed and sat down in his armchair across from John.
John looked at him expectantly.
"Charlotte is my birthname," said Sherlock. "I changed it after I got top surgery when I was twenty-three." He winced slightly, expecting a negative response from John.
John simply nodded. "Oh," he said. "Okay."
Sherlock looked at him strangely. "You-you're okay…that I'm…you know?" he asked, stumbling through his words.
"Of course," said John. "Why wouldn't I be?"
"I dunno…It's not a very widely accepted thing," said Sherlock quietly.
"Well you're the same bloke you were before I looked through that album," said John. "You're still a man even if you haven't got a dick."
Sherlock smiled lightly. "Thanks," he said quietly.
"Don't have to thank me for not being an arsehole," John said lightly. "Tea?" he asked, standing up.
"Yeah," said Sherlock. He stood and followed John into the kitchen.