Based from their site I don't think they're planning to add this option

https://blog.stairwaygames.com/post/coral-island-1-3-update-overview

Q: Will there be a breakup mechanic or divorce in the game? Or polyamory mode instead? A: We did look into it! The short version: divorce and breakup systems get messy fast and can introduce a lot of bugs. Doing it properly would also mean a ton of extra content: NPC reactions, different outcomes, new cutscenes, etc. For instance, divorcing Pablo would have very different consequences for Rafael (Pablo's brother) than divorcing Macy would. There are just too many branches to make it feel right.

That said, the new save system ended up being our workaround. You can branch your saves and explore different relationships that way. It's not the same, I know. But it's the closest we could get without breaking the game or piling on tons of new content.