I seem to remember that sometime in the past few years, the City of San Francisco had an ordinance that all employers had to include gay partners in employees' insurance. The Abp of San Francisco tried to work it out that Archdiocesan employees could designate one person as co-beneficiary on their plan, no questions asked about who that person might be: wife, husband, son, daughter, gay partner, business associate, or random-person-on-the-street.
If I'm remembering correctly, the City's response was: no, not good enough, nyet, ningun, nada.
But admittedly, San Fran is particularly narrow and bigoted that way.
I’ve also suggested that insurance policies might, in place of “employee and spouse,” have “employee and additional adult resident.” That could be a cohabiting nonmarital romantic partner, a parent, a sibling, an adult child, other family member, or whatever. I don’t think that the costs in insurance payout would be greater than “employee and spouse,” because if you limit it to a household resident, a single employee couldn’t add a non-resident parent, for example, to his employer’s policy.
I think it makes sense for the law to recognize that there are other household configurations besides husband-wife-children ... and there always have been. Better, from the insurance standpoint, simply to separate insurance from employment entirely, though.