How do married gay couples address each other?

Solution 1:

The word wife means "woman". In the context of a marriage, then whether same-sex or different-sex* it means the woman one is married to, and always has done.

The word husband meant the man who is the master of a household, but this has moved to having less hierarchical implications a long time ago; not just with the rise of the Women's Movement in the last century, though that obviously had massively increased the changes in how we consider the term.† As such, it means the man one is married to.

So, assuming either a cissexual partner, or a partner that identifies as either of the binary of man or woman, then you call them a wife if they are a woman and a husband if they are a man.

Non-binary identifications vary widely, and so can only really be considered on a case-by-case basis. However, spouse covers same-sex, and different-sex marriages of cis, binary trans and non-binary trans people of all sexes, and so can be used as a catch-all.

*Every time you call same-sex marriage "gay marriage" a bisexual loses their wings.

†Calling the woman in a man-woman relationship "his woman" and the man "her master of the household" may seem a bit sexist. In fact it was very sexist indeed. This was a thousand years ago, after all.

Solution 2:

I read a quote somewhere a few days ago that it shouldn't be called gay marriage but just marriage as there really is no difference.

They call each other husband and wife depending on the gender. That means a male couple would be husband and husband, a female couple wife and wife. If one of them is transgender or similar it's a bit more complicated and up to the couples preferences.

Solution 3:

"Husband" really just refers to a male parter in a marital relationship, so they would both be husbands (one being a wife would be incorrect because, similar to husband, wife refers to a female partner).

Solution 4:

In the news:

The Wall Street Journal reported that Broadwell decided to publish the announcement from a local resident who was united with his partner in a civil-union ceremony in Vermont...

same sex brides and grooms... husband, wife or spouse... (Same-Sex Marriage: The Cultural Politics of Love and Law)

Ontario politicians mourn with George Smitherman after his husband’s death...

Mary Cheney and her wife sharply criticized a comment by Ms. Cheney's sister, Liz Cheney, a candidate for the Senate in Wyoming.

So it really isn't a big deal.