A/N: Stay with me, I know these past few chapters have been more or less information dumps, but I wrote it like that so John would be a little stunned with the suddenness of it all. So just take your confusion and surprise, and transfer it to John's character! Enjoy!
"Again?" John asked.
"There was already a third Holmes, John." Sherlock said. "They adopted him just a few months after me, don't ask Mum, Dad, or Mycroft about him. We're forbidden to speak of him. They've disowned him. He's dead."
"So they disowned him because he's dead?" John asked, now thoroughly confused.
"No, was the manner in which he died, not the fact." Sherlock said. "He always was the wild child, wilder than me even. He was the one that introduced me to drugs. He had fun doing just about everything he wasn't supposed to. He kept experimenting, taking more and more, until he overdosed. I was there, I told him it was too much, but I didn't stop him. I don't remember why now though. Anyway, he overdosed, I called 999 and tried to save him, but he was gone before the ambulance ever got there. Because of the reason he died, we're no longer aloud to speak of him. My parents are convinced it's bad for the public image." Sherlock rolled his eyes at that. "They refuse to believe he ever existed."
"What was his name?" John asked.
"Deleted it." Sherlock said passively.
"You deleted your own brother's name?" John said in disbelief. "How did you remember the story then?"
"I deleted his name, not the story." Sherlock said. "I always delete the names of the dead, but I keep their stories. That's why I go into my mind palace after a case, and why I refer to them as 'the victim' from then on. It makes it easier to detach myself from the situation."
"So you do, in fact, feel empathy for them?" John asked.
"Not for the victim, no, they're dead. Their families however, of course, you'd have to be inhuman not to. So to look at things objectively and to investigate thoroughly without bias, I delete the name and turn off my empathy. Don't you do that?" Sherlock said.
"Uh- no, I don't." John said. "Most people can't just turn empathy on and off like a tap."
Sherlock hummed.
"I guess I don't switch it off so much as I just… ignore it. I leave it floating around in my Mind Palace." Sherlock said. "I don't really feel it so long as I don't consciously think about it."
"You know Sherlock, to others, it sort of looks like you don't feel empathy at all." John said, cautiously.
"I am aware." Sherlock said.
"Then why don't you explain what you're doing?" John asked.
"Because they never bothered to ask." Several minutes of silence passed before John noticed that Sherlock was gripping the steering wheel so tightly that his knuckles were turning white. Not that they were that far from it to begin with though.
"I can't read your mind Sherlock." John said. He could tell Sherlock wanted to speak but had refrained from doing so for some reason.
"I have absolutely no clue how to handle this." Sherlock stated.
"Well, first of all, relax." John said. "You're cutting off blood circulation to your fingers." Sherlock's grip loosened only marginally. John picked his brain for an answer to this problem. After ten minutes, he spoke.
"I think I have an idea." John said. Sherlock looked at him expectantly.
"Chances are, your parents haven't told him much about you, and he won't know what to expect. Try to behave as Mycroftly as possible, but drop the facade when you're alone with him. Be real with him."
"That might actually be worse than if I remained the same way." Sherlock said.
"It will work fine, Sherlock." John said. "People are my thing, not yours. I know how they work. Trust me on this."
"I do."
This was one of those rare moments when Sherlock dropped the arrogant persona and showed his true self. These past few days Sherlock had been the most emotional John had ever seen him. As well as the most stressed.
"Just relax around him." John said. "Just pretend it's just you and me at the flat."
"I can't, John." Sherlock groaned.
"Why not?" John asked.
"Because you're relaxing." Sherlock said.
"Go under the assumption that he is too." John said. "Go in believing that he's going to be your favorite person in the world."
"Hmm…" Sherlock hummed. "One of my favorite people…"
"How many favorite people do you have?"
"Not counting him, two." Sherlock said.
"Who?" John asked.
"You and Mrs. Hudson." Sherlock said.
"Me?" John said, surprised. Sherlock nodded, while squinting ahead at a road sign.
"Why?" John asked.
"Because…" Sherlock hesitated, as if he didn't know the reason. "I don't know, you're just… you."
Sherlock turned the steering wheel to the left
"Almost there." Sherlock said.
Sherlock once again appeared entirely at ease, but John seemed to have learned to recognize a certain tension in him, a certain stiffness that indicated anxiety in the detective. John wished he knew a good way to comfort Sherlock, but the best way he had figured out was to simply be near him. To sit in his chair when Sherlock was in his. Or to sit across the couch or table from him. John wasn't sure why or how this worked, but it did.
"Thank you-" Sherlock said, out of the blue, "for coming with me, I mean."
"Any time." John replied.
Sherlock took a deep breath and pulled into the enormous circle drive.
A/N: Ooh... Now isn't this an interesting development? Another Holmes brother? Only this one is dead. Why didn't Sherlock stop him from overdosing? What part does Sherlock not remember? What if he deleted it on purpose? And how will Sherlock's first meeting with his parents in twelve years go? Reviews please!