This was posted in sherlockbbc-fic in response to the prompt from Anonymous:
"Mycroft has always had to pretend to be normal his whole life - in reality he's exactly like Sherlock only he's better at hiding it and blending in. As a result he's always been the most popular out of him and Sherlock, the onef their parents prefered, the one who got further up the career ladder. He's never had a problem with it before - and has been happy to be what he sees as "out doing" his little brother - until he realises that Sherlock and John both genuinely care about each other and is jealous because Sherlock has something real that he doesn't have"
Disclaimer: I own nothing and make no profit. Quotes are property of Gatiss & Co.
Mycroft has been able to lipread since he was four. He's been able to access the security camera footage all over London since he got category five clearance seven years ago.
He's watching the cameras on Berwick Street this evening. More specifically, he's watching Sherlock, his wayward younger brother and that soldier fellow. He's tracked them through a laneway and on to D'Arblay Street, running after a taxi. They've been travelling at a full run, over the roof tops and down fire escapes from Northumberland Street. He estimates it's 1.2 miles of route undertaken in less than four minutes. A small part of his brain is calculating their average speed; the bulk of his brain is otherwise occupied.
He's fulfilling his promise to Mummy, "keeping an eye on Sherlock". It has always been his job to do so and he submits to the request with all the grace of a favourite child and in doing so, he is favoured all the more.
He's been fulfilling that same promise to Mummy for over twenty years now. Ever since it became clear that Sherlock wasn't like the other children at playschool; he was three.
Sherlock was always a trying little boy. Mycroft had himself become accustomed to the idea of being an only child when at seven, he found himself in the role of the elder brother.
It's always been that way for Mycroft. It's easier to make sense of all the information if it's labelled and placed in its own category and it's no different with people: a different performance for different audiences. He is the dutiful son, the diligent student, the dynamic "civil servant". It's not challenging for him. He knows that he only ever had one potential rival, Sherlock, but he has proven less than Mycroft had believed he could be. Never a rival at all - not in school, in university nor even in their mother's heart. This is why it's easy for Mycroft to fulfil that promise. Yes, partly, he is playing the role he set out for himself (though he does not accept that there was any advantage in having the seven year start) but mostly because he sees, observes and understands in a way Sherlock simply can't. Or won't. Same effect.
Mycroft can admit to himself, in his more honest moments, that Sherlock is quite probably as clever as him. Indeed, Sherlock has never made any attempts to conceal his own brilliance nor miss an opportunity to impress it on anyone. And that's why Sherlock will never be a true rival for Mycroft, why he'll never be first.
Because the question of who is first in any case is determined by people and their opinions, not by intelligence quotient. That's why Sherlock did not exceed at the various schools he was transferred into and out of. He had to be right, even if it meant proving everyone else wrong, his teachers, his peers and, on occasions, their parents. Not the way to make yourself needed, wanted or popular. Mycroft understands the need though he doesn't let it consume him. He's a social chameleon he thinks. He's used to holding it in and can do so without getting an ulcer. It's so much better to be accepted than be, well... oneself, he supposes. At least until you can become established. But although Mycroft understands what drives Sherlock, Sherlock has never understood what drives Mycroft and Mycroft knows that Sherlock views him with contempt for living his life behind that veil.
Mycroft feels no bitterness to Sherlock though he admits that he does pity him. Mycroft's got the job, got the power and the control that Sherlock will never have.
On the camera, he sees Sherlock and the soldier walking away from the taxi. Sherlock's made a mistake, he looks frustrated, glancing up and down the street. He's brought the limping soldier on an evening run and for no good reason. He notices Sherlock is not meeting his companion's eye. Mycroft smiles.
The soldier is pulling the badge Sherlock used from his gloved hand. Lestrade's no doubt. Mycroft snorts; he's alone in his office so no one to think him strange. He watches Sherlock's lips, watches him admit that he pickpockets Lestrade when he annoys him. Mycroft wants to shake his head - you're not meant to admit those things. Mycroft knows better. He would never admit to doing something illegal and he has learned that annoyance towards other people ought to be concealed. Mycroft pans the camera to watch for Watson's response. He watches as Watson looks up at his brother and breaks into a laugh. Mycroft is perturbed. Sherlock looks equally baffled.
"Nothing. Just 'Welcome to London'" Mycroft can imagine the words in Watson's voice. He switches to the other camera and catches Sherlock's lips curve upwards at the edges. He's smiling. Mycroft recognises his smile - Sherlock is flattered by John getting his sense of humour. The scene plays out
"Got your breath back?" his brother mouths and then, when Mycroft switches cameras he watches Watson respond: "Ready when you are". They turn together, their side profiles to both cameras and dash away. There's symmetry to the last frame, a balance to it with two dark figures running into the lilac lights of the city together.
Mycroft can't afford to make mistakes, not in his position. Lives are at stake, as he reminds himself daily when he gets bored with his subordinates and their little lives. He hasn't cracked a joke in years; his current role doesn't come with a sense of humour. Sherlock used to appreciate his sarcasm but that was before his contempt had taken root. These days, Sherlock is more likely to simply scowl and respond with some defensive, derogatory, snide remark about Mycroft's work or the traffic, or both. He knows if he were to drag his PA around the city on foot on one of his hunches, she would not be in any kind of a mood to appreciate his hitherto fore concealed sense of humour.
Mycroft switches the monitor off. It strikes him then, how Sherlock, with no social skills to speak off and without practising any restraint on what he says or does, has made himself a friend, a real one this time, not a skull nicked from Bart's morgue. And Mycroft knows John Watson is and will be a friend to Sherlock, better than Sherlock or the man himself knows. He turned down the money, without a figure and with less than twenty-four hours' acquaintance. Mycroft wasn't lying when he told Watson he was very loyal very quickly.
He should be happy for his awkward and difficult brother. His promise to Mummy is even less of a burden to fulfil with John Watson in the picture. But in his gut there is for the first time since he became a brother, a sickening, burning sensation, that he recognises as envy. Is this how Sherlock felt year after year when their tutors, headmasters and parents praised him and screwed their faces into disapproving frowns when they looked at Sherlock?
Sherlock has been only himself and has a real friend. Mycroft has been everything to everyone and has nobody but himself.