Chapter Text
When Jyushimatsu went into his first heat, a week before his sixteenth birthday, his parents had been ecstatic.
Jyushimatsu hadn’t been. At least, not at the time. An omega’s first heat is always the hardest, and he wasn’t prepared for it. It had been an uncomfortable and disorienting time for him. His siblings hadn’t been very happy with it either; he’d been moved into a separate room during the course of it, under the watchful eye of their mother, and his absence in their shared bed left a gaping hole they all felt intimately.
The heat had only lasted a week, thankfully, and it wasn’t long before Jyushimatsu was back to his excitable self, with triple the excitement. It was only the start of this particular brand of puberty for him, but already the world had seemed so much different with the aid of his, now enhanced, senses, and he loved it. Naturally, he did his very best to share all the exciting new things he’d started noticing with his brothers, but it had done less to enlighten them than it had to make them impatient for their own changes.
Luckily, they hadn’t had to wait long; two weeks later Jyushimatsu woke to a strange new scent in their bedroom, and it had taken no time at all for him to figure out it was coming from Choromatsu. He was immediately excited, even as the scent triggered a weird feeling in the pit of his stomach, and he had spent a brief moment debating over whether or not to wake Choromatsu before he clambered out of bed, going to fetch his parents instead. If the change Choromatsu was going through felt anything like Jyushimatsu’s first heat, he was sure his brother would want to be under their parents’ care as soon as possible.
Their parents had been just as happy about Choromatsu presenting as an alpha as they had been Jyushi presenting as an omega, and their joy had only grown as each of their children continued to steadily present over the following weeks. Ichimatsu had been next, following Choromatsu’s lead in presenting as an alpha, followed by Todomatsu as an omega, and finally Osomatsu, once again an alpha. If he’d been bitter about being the last alpha to present, he never said anything.
Karamatsu had been the only Matsuno child who didn’t present as either.
At first, his parents had figured that maybe he was just a late bloomer; after all, the brothers were identical. The chances of all but one of them presenting were very slim. They’d held onto that hope, even as the sextuplets’ seventeenth birthday rolled around, and Karamatsu made peace with the fact the he was likely never going to present.
By the time he’d turned eighteen, even his parents had accepted that their second son was likely a beta.
And that was fine. Really, it was. They had two omegas and three alphas, more than enough to guarantee plenty of grandchildren. One beta child was no reason for concern.
Karamatsu was fine with it too. Sure, his brothers’ changes had meant that they felt and sensed things differently than he did, and over the years he often felt out of the loop when they were together, but that was okay. It was okay that, as they climbed the ladder to adulthood, his brothers’ started noticing him less and less. It was fine that their relationships with each other began developing into something he could only dream of being a part of. He loved them all, and any petty jealousy he may have felt wouldn’t change that. He was happy for them. Happy that they would have a much easier time succeeding in life than he would; happy that they would never have to worry about being alone for the rest of their lives, because they had each other, so why would they ever need to seek mates elsewhere?
If Karamatsu had ever worried about his own fate, in that regard, he never brought it up to anyone. It would have been obvious to anyone who paid attention, anyway.
The following years had flown by, and Karamatsu settled into his (invisible, irrelevant, useless) role in his family, and he’d been happy. He was content. Really, he was. After all, his family were happy, and he and his siblings were all still allowed to live under their parents’ roof, so why would he ever hope for anything different? Life couldn’t be better.
Karamatsu is twenty-one when he goes into his first heat, and everything changes then. He’s not sure that’s necessarily a good thing.