i can never write a soulmates au cause i very quickly stop thinking about romance and start thinking about the sociological implications of a world where soulmates are a confirmed verifiable thing
is casual dating a thing in a world where everyone has a soulmate out there somewhere? is it frowned upon? is there a movement of people fighting for the idea that you don't HAVE to wait for your soulmate to find true love? is it considered queer to be in a non-soulbound relationship? how does polyamory function? how about aromantic people?
is it guarenteed you'll find your soulmate within your lifespan? are you drawn to find eachother even if you're born a million miles apart? if it's the kind of universe with physical soul marks (ie. matching moles, first words on skin), are there medical options to change or remove your mark? would it be considered a tabboo? could someone fake a soul mark? could you catfish someone by pretending to match them? isn't there some kind of inherent horror in knowing destiny has entwined you with a stranger?
What happens when there's DV in a soulmate marriage? what are the laws on soulmate divorce? If everyone had a destined partner then there would be so much backlash on people divorcing people that were their confirmed soulmates! If tis a DV situation, how do you explain that the person who was supposed to love you the most in the world did this, how do you get beleived? Where do you get support?
What are the social implications for having children with someone who isn't your soulmate, are those kids considered lesser like bastard children were in the past? Do people who get pregnant outside of soul-mating get sent to women's homes like Catholics did?
What happens to widows, is it acceptable to remarry AFTER your soulmate dies? Is it only acceptable to remarry other widows? What happens if your soulmate dies as a child? Do you know if they die? If there is some sort of marker that tells you they're dead, would people find ways to fake that in order to serial date without the social backlash of not looking for your soulmate?
All of the above, yes! Soulmate AUs have long bothered me on many of these points.
Discussing this post with bf, however, he suggested a version of the whole soulmate concept that might answer a few of these things, ignoring the weird deterministic angle perhaps?
Instead of a soulmate mark appearing at birth, it only develops after you've been dating/close to someone for a good while. Let's say a year on average, give or take. In this way it's more a confirmation of compatibility than a mark of destiny from the get-go. Let's also say that the mark can develop no sooner than biological puberty if you want an evolutionary link, or if you're going cosmic/mystical/the work of a god, it develops around whatever the social age of majority is (or maybe the earliest it develops is the social age of majority, chicken or egg style).
As such, aromantics need never have or develop one, polyam groups might get whatever makes sense as a group, and if you assume that whatever universal force or omnicient love god is in charge of all this is concerned with the happiness and well-being of those involved, then presumably DV could be circumvented in genuine cases of soulmate connections. And at the very least you're not being bound by destiny to a complete stranger from the beginning of your existence.
Now this still has worldbuilding implications. Weddings might not have quite the same social weight of making oaths to each other - maybe once you get those marks, you're considered good as married and all that's left is to fill out the paperwork on it for the legal side of things and throw a celebratory party for the social side.
Maybe it's still considered abnormal if you never, ever develop a mark. The happy utopia for couples who face societal struggles to be together in reality still doesn't necessarily work out particularly well for aromantics, given the heavy romance focus of this worldbuilding. I don't think this can be fixed except with the happy little bandaid that says everything is ok for everyone, actually - not a very realistic answer.
If a couple dates for years and years and never develops marks, do they break it off as something that'll obviously never work out? Stay together hoping it might one day change? Go to some shady tattoo artist who can more or less reliably fake the marks in order to get married even if the universe seems to be saying they shouldn't?
Can these marks change or fade over time? People grow and change and this doesn't stop just because they've married each other. It's possible to just grow apart, to lose compatibility. Is a changed, faded, or lost mark simply taken as evidence enough to grant an easy divorce? Is it regarded as some kind of moral failing by society? (grounds for cultural differences there, I think) Again, can it even happen in the first place, or is the judgement of the Universe/Love God doing this simply that infallible?
If you're widowed and begin to date again, maybe you can start developing a new mark with someone, whether they had a previous soulmate or not. Do the marks change due to death? Do they remain in some form forever or do they fade away with time?
...
You know, all this said, I think that part of why the whole Predestined Soulmate AU thing rarely works out when you really start poking at it is this: love isn't just about feelings. It's about choice. It's choosing another person, choosing to communicate, choosing to cooperate, choosing to stay with each other or choosing to break apart.
Soulmate AUs are pretty little surface level fantasies where you cannot ever make the wrong choice, and therefore nobody can deny you that choice...but there is no choice in that part, is there? It's really just a cosmic-level arranged marriage, and sure, you can still choose to love that person, but you never chose the person to love.