here’s the thing. marriage is a legal contract and i fr dont know why anyone thinks of it romantically (now). the romantic part is “i love this person enough i think i’m going to want to legally share my life with them forever” but it is still Legally Sharing Your Life With Someone and if you don’t want to do that, it doesn’t mean you don’t love them a lot, just like not wanting to get their name tattooed doesn’t mean you don’t them love them. it’s just not something you want to do, for any number of reasons. i feel like im going insane sometimes with the way people talk about marriage.
anyway all that is to say, even in a society where it is illegal to marry someone other than your soulmate, there are plenty of reasons for people to not want to get married - particularly for the elite, who have the most influence over law and might have to ‘worry’ about their soulmate being a commoner that they don’t want to Legally Own Half Their Stuff By Default. so i think what marriage is legally, if it exists in a universe at all, would still exist in soulmate universes. even if you do want to be tied to your soulmate… when does that kick in? the second you meet them? Some arbitrary date afterwards like “one year from meeting to get your lives together”? when you turn 18? when if you dont meet them until youre 40? so yeah i think it still exists lol
in the mass effect au, how people treat marriage socially/romantically was covered by the marks, and legally they didn’t have the same kind of concept Exactly. you could sign off to own a home together - unmarried people can do that irl too its just hard to get approved lol. if you had a child together legally you would split parentage anyway. if you wanted to “adopt” a kid you could adopt a part or whole of their parentage regardless of relationship status. so yeah they just don’t have marriage but they have some legal processes to get some of the same functions that are practical - but those things could go to different people, too. one person you’re mated to, another you split a child with, a third you own property with, etc. it’s like… modular i guess. in practice, usually you were owning property and having children with your mate lol, but not always and magicats are more aquainted with “nontraditional” families as a result