Wiktionary
co-husband
n. In a polyandrous marriage, another husband of a man's wife.
Usage examples of "co-husband".
But I’m married to three of your descendants - Tamara, Ishtar, and Hamadryad - and co-husband to another, Ira Weatheral.
Two of my wives and one of my co-husbands are descended both from Nancy and from Woodie.
One of my co-husbands, Ira Weatheral, also from Nancy and Jonathan but from Woodie, too—and named for your father, not for Ira Howard—is over four hundred years old.