A lot of things happened to Mycroft when he was seventeen. He graduated from Eton, he got accepted into Oxford, he met his wife - those were the highlights of his year, the latter more-so by far. In fact, the only good thing to happen to him at seventeen was his first meeting his wife.
Graduating from Eton hadn't been all that brilliant. His parents hadn't been particularly impressed. It's not like he did it a couple years early, like Sherrinford had, or in spite of all the troubles Sherlock seemed to encounter. In comparison to his brothers, Mycroft's school years were no more impressive than your next garden-range gifted student, and his parents saw no reason to treat it as if it were anything more.
They were similarly unmoved by his being excepted into Oxford. Honestly, it would have been a shock and quite the embarrassment if he hadn't been. And really, it wasn't anything all that special, that is to say, Sherrinford was just 15 when he got in. They were also a bit distracted at the time, trying to fit Sherlock into his newest school after the regrettable incident with the last one's chemistry lab.
As such, they hadn't had the time to drive him up to Oxford themselves, and really - they were busy people, Mycroft wasn't a baby and they'd already learned from doing it with Sherrinford that there wasn't all that much for them to do other than provide a lift, so why take a day off work when they can just pay someone to do it for them?
Mycroft steadfastly hid how hurt he was by their decision to have one of mother's driver's take him up as an alternative, choosing instead to be grateful for the pat on the shoulder and peck on the cheek he got from them as they headed off to work.
Unfortunately, things didn't get all that much better for him once he finally did get to Oxford. He was living in the college, like most of the other first year undergrads, but none of them seemed to take all that much of a liking to him. That's not to say they were horrible to him, in fact, there was no outright hostility directed towards him at all. It's just they weren't all that welcoming either.
Under normal circumstances, Mycroft wouldn't have minded, in fact, he probably would have found the situation ideal. Unfortunately, at the time, his circumstances weren't quite normal. He was apprehensive about the whole situation, as people always are with new things, he was lonely (just like in school) and he was really quite horribly homesick.
All the other students called their families, to stay in touch. Mycroft had tried doing this himself but had gotten a stern talking to from his father, who'd insisted he man up and deal with it ('Sherrinford was never like this, I'll tell you that'). That conversation was quite enough to dissuade him from attempting that small comfort again.
He wrote to Sherlock, but got a scathing letter in reply informing him that whilst Sherlock was being held captive in his newest prison (read: school) and Mycroft was out and about living the big life, he can shove his letters right up his - well, he wasn't all that open to communications either.
And of course, Sherringford was out of the question. Mycroft knew from experience that situations always seemed to get worse for him whenever his big brother was involved.
Suffice it to say that by the time he met Iris, things had gotten a bit too much for him.
He'd been sitting on his own in one of the parks in the more residential part of Oxford, as far away from the university as he could get. The idea had been to go for a walk, to clear his head a bit. It had quickly dissolved into his simply finding a quiet spot to have a bit of a cry in and be done with it.
She'd sat down beside him and asked if he was alright, rubbing his back when the tears insisted on falling in spite of his insisting that yes, he was absolutely fine, no really, don't worry about him he was fine.
When he finally did get enough of a hold of himself to stop blubbering like an absolute idiot, she insisted that she take them both out for dinner, because she wanted the food and frankly, he looked like he could use the company.
They ended up spending the night together, talking about everything from their studies to books to that time Mycroft tried to teach Sherlock astronomy.
He asked her if they could meet up again, at some point, if she wasn't busy and just as friends of course, he wasn't presuming anything he just liked her company really.
Fortunately, she quickly kissed him on the cheek and insisted that yeah, she would quite like to catch up again, but she would rather it were a bit more than just friends. Mycroft made his way back to his room grinning like an absolute loon that night.
Suddenly, Oxford didn't seem so gloomy when he had Iris to study with, to walk to and from lectures with, to just generally be around. She brightened up his day, as cliched as that sounded. And what was more, he thought that, in spite of how completely illogical and potentially disastrous such a condition could be, he was utterly in love with her, the sort of love that makes you want to shout so everyone could hear about it or made you feel like you could fly.
He didn't say any of that out loud of course, Mycroft was not the fanciful sort. But Iris had always had a way of knowing the things he left unsaid, and she had no qualms with informing him she felt the same.
They shared a flat during their second and third year at Oxford, and then rented another in London once they graduated. It wasn't nearly as grand a living as his parents had expected from him, and it certainly didn't live up to Sherrinford's classy lifestyle, but it suited them and that was more than enough for Mycroft.
Four years later, he asked Iris to marry him. She'd rather enthusiastically agreed.
It was a small, private wedding. None of Mycroft's family turned up. His father had died a few years earlier in a car accident on the way to work and his mother had fallen ill just after their engagement was announced and simply didn't get any better. Sherlock was god-knows-where, no doubt high as a kite and antagonising everyone he came across, and Sherringford considered their relationship rushed, doomed to fail and resolved to have no part in it.
Mycroft didn't mind though, because Iris was there, beautiful as ever and promising to spend the rest of her life with him, and accepting his pledge to spend the rest of his with her. Everything was just brilliant in his eyes.
They'd decided that they should focus on their careers first, before even trying to start a family. Having children as young as they were would have been quite detrimental to both their plans. So that's what they did. Mycroft slowly but surely (and always quietly) made his way up in the government until his influence surpassed even that of his mother's (although she was no longer around to be proud of him for that) and Iris was quickly becoming one of her paper's best journalists. It didn't pay much admittedly, but it worked for them.
It wasn't until quite a few years later that they felt ready to start trying for kids. 12 months after that decision was made, Basil Holmes entered the world. 3 years after him, his twin brothers Alfred and Harold joined them as well.
Predictably, things got harder, financially, as the family grew bigger and the boys got older. In spite of Mycroft's practically being the government by that point, he was still being paid a basic civil service wage. It made things harder but it was better in the long run. Being paid appropriately would only draw unwanted attention to his family after all.
And Iris was only a journalist, she loved the job but like Mycroft's, it wasn't really a bread-winning career.
They made it work though. They scraped and they saved and together they managed both to live comfortably and to maintain the illusion of the posh lifestyle Mycroft's reputation required for his work. They lived in the right part of town, wore the right kind of clothes, the kids went to Devonshire House and Basil was well on his way to getting into Westminster (thank god for scholarships).
It certainly wasn't easy, but it was good and Mycroft loved it just the way it was.
And then Iris started to get sick.
Mycroft had wanted her to go to the doctors immediately, but she insisted that it was fine and reminded him that it was just flu season and that they both knew that on the rare occasion she actually got sick, her body didn't do things by halves. Grudgingly, Mycroft let it go.
But she just didn't get any better.
And then the abdominal pain started and by the time the doctors confirmed what was wrong, the cancer had already spread too far. Treatment would have only given her a little longer, it wouldn't have cured her.
Iris refused chemotherapy, determined to spend what time she had left with them as healthy as she could possibly be. She passed away not too long after the diagnosis was made. Mycroft didn't know whether to be grateful for that or not. On one hand, she wasn't suffering for long, on the other... she was gone.
It was a small, private funeral. None of Mycroft's family turned up. His parents were dead. Sherlock had been overseas, god-knows-where, and didn't learn of Iris' passing until after the funeral and Sherrinford sent his commiserations but couldn't take the time off work. It was just him, some of Iris' workmates and the boys bidding farewell to the beautiful woman Mycroft had once promised to spend the rest of his life with.
Things got harder after that, financially, emotionally, everything was just harder.
He had to maintain the illusion of privilege to keep his position in the government secure. He had to work longer hours and they had to make sacrifices to meet their budget, like the heating, the school excursions and their grocery list.
And that was just the practical side of things.
He was supposed to be helping the boys cope emotionally with everything that had happened.
They'd lost their mother for Christ sake, how was he supposed to make that better? How was he supposed to make any of it better? How was he supposed to help them cope when he wasn't coping himself? How was he supposed to keep things together when he was falling apart.
A mere month on his own and he was already in way over his head. He couldn't do it on his own. Things couldn't possibly get any worse.
But then, of course, they did.