[dragonwriter]

> Three person marriage is likely next.

> It avoids incest taboos and the groundwork has already been done.

It actually hasn't; any two-party marriage uses the same infrastructure without problems, the differences are simply at the front door.

Multiparty marriages need ground up redesign of the rights and privileges, which are all based on exclusive dyadic relationships.

There's quite usable outlines of how the legal infrastructure might support many aspects of multiparty marriages (especially in terms of things like dissolution) in, e.g., the law of business partnerships, but the context and details of the rights and privileges tied to marriage are sufficiently different that there is a lot of work to do define even what a multiparty marriage would mean legally.

Its not a simple equality step that can be addressed largely at the front door like interracial or even same-sex marriage.

[LordKano]

"Equitable division of marital assets and liabilities."

This doesn't require anything special.

Legalizing same-sex marriage required changes on license forms, this will too.

[Jtsummers]

The fundamental change (ignoring issues with the religious) for same-sex marriage really was just the genders specified/described in most legislation and regulations related to marital rights, privileges, obligations.

For multi-party marriage one major issue will be based on this assumption: members can enter into and leave a marriage without dissolving the rest of the union. If 4 people are married and wish to add a fifth, and later one wants to leave, this should be feasible. How will the various assets be combined and removed from the other parties when people enter into and leave this plural marriage?

It's not as straightforward as the current two-person marriage. (Ha! It's not clean for two-party marriages either.) It'd be interesting to see, but it'll require a bit more structure to be set up, or at least more deliberation to ensure that it's not a complete clusterfuck the first time someone wants to divorce their two wives and husband (see also the issue with civil unions before same sex marriage was legalized and the issues faced when trying to dissolve those).

[dragonwriter]

> "Equitable division of marital assets and liabilities."

> This doesn't require anything special.

Right, and how to mechanically achieve this in multiparty relationships on dissolution is what I referred to as having a particularly good model in partnership law, because its done there a lot, and the wrinkles in how it works out have been pretty heavily hammered on over several centuries.

The non-dissolution aspects of marital rights and privileges and how they would apply to multiparty relations (and whether existing explicit rules and legal presumptions built on the premise of a dyadic relationship work, or even make any sense, in multiparty relationships needs to be considered, area by area; for some aspects of this, again, partnership law probably has good models to follow as to how things might be generalized.)

E.g., there's lots of things where spouses have either decisive rights or are necessarily included parties that must each consent, written based on the dyadic nature of existing marriage structure. Whether these generalize to every spouse having the same powers and requirements as a single spouse does now, or whether those powers require a majority of the members of the multiparty relationship, or some other rule in a multiparty case probably needs separate analysis for each of the areas.