A/N: Written for a shkinkmeme prompt: I want a feeder and feedee. I dont care who which is. I just want one.
Mycroft had always loved food, abhorred exertion, and been stockier than his willowy brother. But what no one suspected, not even Sherlock, was that his girth was intentional and very carefully maintained.
It began in university. He often observed the interaction of members of the faculty, and was intrigued to find that the opinions of larger men were given more weight than those of more slender men, even when the larger man was lower in rank or standing. It was a most interesting study, and he continued it for several terms but never found an exception.
As part of his studies, he spent a term working as a clerk in Whitehall, where the rule of size also appeared to hold true. It was just as well, for there were a number of excellent restaurants in the area where Mycroft passed many pleasant meals, to the point that his clothing began to feel uncomfortably tight. When he returned to classes the following term, Mycroft decided to use his size as an advantage. And like any advantage, it must be fully utilised to be most effective.
Spencer had been a good friend for much of Mycroft's time at university, for he had more wit and intelligence than was typical amongst their peers, but he also hosted many splendid parties that were legendary for their abundant quantities of the best foods. Though Mycroft did not say a word about his resolution, a few weeks into the term Spencer slipped him a box of chocolates containing, in addition to the excellent Belgian confection, a message offering his help.
Mycroft turned him down at first. But as the term progressed, he soon found that his efforts to increase in mass were limited by his wallet, his habits, and his limited free time. So when Spencer invited him to dinner at an expensive restaurant, complete with an offer to pay the tab, Mycroft accepted.
What Spencer proposed to him at that meal was an arrangement where he would provide all of the food Mycroft could possibly eat in exchange for the pleasure of watching him eat and occasionally being allowed to physically feed him. As a trial, Mycroft would spend the spring holiday at Spencer's home. If he wished to discontinue the arrangement when they returned to classes, that was up to him. If not, he and Spencer would find a flat to share and continue their arrangement until Mycroft decided otherwise.
Mycroft returned from the spring holiday three stone heavier and happy as a clam despite needing to have all of this trousers let out. During the term he focused on maintaining his new weight and was concerned that Spencer would object, but Spencer was perfectly content to watch (and help) Mycroft consume moderate quantities.
Their arrangement lasted for the rest of their time at university. During terms Mycroft would focus more on his studies than on eating and Spencer would merely ensure he ate enough to sustain him, and during holidays Spencer would lavish him with food and Mycroft would eat it all. Spencer catered to his every whim, and he found the pleasure of good, rich food was only heightened when it was fed to him. Allowing Spencer to see and feel the added flesh on his frame was a logical next step, and if their relationship crossed into territory that was legally questionable, well, neither of them were going to breathe a word.
When they had both taken their degrees, Mycroft was granted a minor position in the Whitehall office where he had clerked. He appointed Spencer as his assistant, so they moved to London and its prospect of many exquisite restaurants (along with the skilled cook Spencer hired to come to their flat).
By the time Mycroft took the job, he was nearly twice the weight he had been upon starting university and he preferred it so, feeling that the bulk gave him an air of command that even his brilliance could not convey. His earlier inference about size and authority was soon confirmed: in an office meeting, a thin, mousy-looking colleague set forward a proposal that the rest of this office immediately criticised. Knowing his colleague was right, Mycroft waited until someone else had made a suggestion and been voted down before he spoke. Presenting his colleague's proposal in a nearly identical fashion, his words were followed by silence as the others pondered; the silence was soon broken by murmurs of agreement.
This one success quickly led to many more, and though Mycroft knew some would object that he had taken credit for another man's idea, he also knew that he would have inevitably found success due to his great intellect. It was only that he had reached it a little sooner this way.