[quote=ImportantNobody]
Perhaps. Even some of that 50% might develop a closer relationship with another women just to spend time with and help close the void. There may be a term for this type of friend, who's like an opposite of a friend with benefits. A person similar to a married couple but without benefits. Then the other percentage of the population just skip all of that and just go all out in the getting married part. After all, it would most certainly be made legal in a lot of places.
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In some places where homosexual marriage is legal, straight people of the same gender will marry for non-romantic reasons. There'd quite probably be a lot of that going on in this world.

I'd assume the term might be something like 'domestic partner'? Maybe 'Housemate'?