I kind of like this...saddle them with all the crazy marriage laws out there. So now when they shack up they are getting married in some states.
They both have to proclaim it to be ‘married’.
There are some partners (even in male-female couples) who refuse to get married.
But maybe now the roommate can get some judge to recognize it after the fact when that person’s family comes calling for their stuff back when their relative dies.