Poor Mycroft. :( I got a sense that Sherlock's annoyance with him was possibly rooted in something that happened in childhood.
Reconnect
"It's partially for this reason that Mycroft and I don't get on very well," continued Sherlock. "We're too similar to each other, even though I'm smarter and less of a…diva."
John snorted. "You have your moments."
Sherlock ignored him. "He never kept his promises, and I stopped trusting him and respecting him as my older brother and confidant. I remember when I was twelve and he didn't come through for me on a matter of great importance. I haven't gotten along with him since."
"He wants to get along with you," John said quietly.
"I know, John," murmured Sherlock.
Prompt was from Javien Deluke, and it was: confidant