John never knew.
He found out when he came back to Baker Street and heard the song Sherlock was composing. It was the most heartbreaking one yet. Worse than when he was bored.
Sherlock stopped and turned to look at John. Had...had Sherlock been...crying? No way, this must be some practical joke. An experiment went wrong and he got something in his eye. Sleep deprivation.
"John, I thought you said you were coming over at six." Sherlock held his violin in the crook of his arm, staring at his upright bow.
"It is six, Sherlock. Six fifteen to be exact."
"Oh, I've gotten carried away, sorry." Sorry. Sorry? Sorry?
"Who are you and where is Sherlock." John seriously reached for his gun.
"John it's me. You're late because Marry wanted you to look at layouts for the nursery and you two had a fight which ended in you giving her pickles."
"Then what's wrong?" Sherlock put his violin down and walked down the hallway, speaking no words, and slamming his door. When he called Mycroft he had screamed at John and hung up.
Only when he consulted Mrs. Hudson, had he found out the answer.
"Why are Sherlock and Mycroft so moody today?"He asked as Mrs. Hudson poured his tea.
"You don't know? After all those years of living with Sherlock?"
"Know what?"
"Sherlock had a sister, a very beautiful one named Amelia, and she died a very year before you came along. Sherlock spiraled in and out of rehab and such. She would always help him solve cases, solved mine as well. Such a shame, such a shame." John was taken aback. After all these years, he had never know. He had never know that Sherlock had a sister, that he had mourned her death with substance. He had always thought that that came with depression he had gotten or the over work. No, it was because the man really had a heart inside that platinum shell.
"How, how did she die?"
"No one knows, not even Mycroft. Only Sherlock knows and he will not tell anyone."
"How could a man keep a secret like that to himself?"
"He's Sherlock," That was the only explanation John ever got.
