Sherlock comforted himself that really it was inevitable. There had never, as far as he knew, been two true Holmes in the same generation before. One terribly precocious child with no social skills was usually enough. But somehow he’d happened and now there were two of them and that wasn’t meant to happen and he’d realised when Mycroft came home for the holidays after his first year at University just why it wasn’t supposed to happen. They’d always had a connection, stronger than any he’d ever observed between two individuals, but when Mycroft stepped through the door, tall and just a little bit chubby and dressed in an impeccably tailored suit Sherlock’s mouth had gone dry and he realised why it was he never had crushes on girls from the school next door, or the prefects or even the younger masters like the other boys did. He didn’t need school boy crushes when he was already in love. This was why there was only ever one of them in each generation.
He’d been uncharacteristically quiet that holiday, so much so that even his father had commented. The truth was that the moment Mycroft stepped into the room he took up all Sherlock’s attention.
It wasn’t just sexual, though he was honest enough to admit that he wanted Mycroft in a way no brother should, it was some force that no one had yet found a name for, like gravity but just between the two of them.
It took him two years to pluck up the courage to approach his brother, but when he finally did Mycroft had just opened his arms to him and called him darling, something no one had done since he was a baby. Most people found him too angular for pet names, but Mycroft, wonderful Mycroft who was all softness petted him and loved him and treated him like the most precious thing in the world.
And Sherlock thought maybe it was a pity that there was only meant to be one Holmes in each generation because what they had was so perfect and lovely. And then Mycroft had been hurt, attacked by a rival, and he had been fine, no one ever got one up on Mycroft and the other man was dead, but Sherlock suddenly understood in a way he never had before. There was only ever one because no one was supposed to love anyone this much, this fiercely. It was too much for one body to cope with, it felt like his heart was burning its way out of his body.
They’d spent less time together after that, both aware that the intensity of the thing, the sheer burning heat of it could burn them both, destroy them even, though they could never keep apart for long.
Mycroft had thrown himself into his work, and Sherlock had found a friend, something he’d never needed or wanted before, and that had helped to fill the emptiness that engulfed him a little. John was kind and patient and really very good at keeping up with him compared to most normals, but not so good that he noticed anything odd about his and Mycroft’s interactions. He simply thought Sherlock’s rudeness was childish resentment of an overbearing brother. He could never see that it was part of a bigger game.
Their relationship was odd, unhealthy even, Sherlock recognised that. They were too close, too devoted and at the same time, too antagonistic. Sherlock delighted in annoying Mycroft, needling at him until he snapped. Above all else Sherlock loved getting under Mycroft’s skin, breaking his careful façade. It spiced up their sex lives no end, Sherlock was more than a little in love with pain and danger so long as no one expected him to behave himself, but more than that, he loved that he was the only one who could get under Mycroft’s façade and see the beating heart beneath, the fierce churning emotions that most people wouldn’t have believed him capable of.
When Moriarty had snarled, in that mad voice, that he would “burn the heart out of you” Sherlock’s felt like someone had replaced his blood with ice. Surely he couldn’t know… But then Moriarty’s eyes had slid to John, wrapped in Semtex and with the red dot of laser sights flickering on his forehead and Sherlock felt sick with relief.
Later he felt guilty, really truly guilty for the first time in his life, because John was kind to him and he did love him, even if it wasn’t the same way, and he knew academically that John was a good man, not that such things bothered him, and that the world would be a poorer place without him.
Unable to sleep while he churned with this unaccustomed emotion he got up and woke John. John blinked owlishly at him, still half asleep as Sherlock asked all in one breath, “if someone were too threaten someone and you though they were threatening someone you loved and then you realised they meant someone else, even if it was a friend, is it bad to feel relieved?”
John stared and then said slowly, “No. No, that’s not wrong. You can’t govern how you feel. But what…”
“Doesn’t matter,” Sherlock answered, and then added as a new thought popped into his head, “I’m going out. Need to see someone. Don’t worry, I promise I’ll get some sleep tonight.”
Sherlock didn’t bother stopping except to throw a coat on over his pyjamas and stuff his phone into his pocket before he rushed out of the door, hailed a cab (without any problem as usual), and directed him to Mycroft’s very secure, very secret, London town-house.
As always Mycroft opened the door for him just a moment before Sherlock could knock. Mycroft looked him up and down, assessing his mental state, and then opened his arms to him, uncaring that they were standing on the doorstep in a clear view of everyone who happened to look their way. Compared to the pain he’d seen in Sherlock’s eyes, Mycroft’s reputation mattered not a jot to him.
“I’ll tell you everything later,” Sherlock promised his brother, though he knew Mycroft would already know the broader details, “but for now I need you.” He tapped his skull irritably. “Make it stop Mycroft. Make it quiet.”
Mycroft’s only answer was to kiss him lightly on the forehead and draw him inside the house, locking the door tight behind him.