That would probably be termed an "N", with a relationship between each husband and wife and then the relation connecting one husband to the other wife. If relationships form between the other parties as well than you might have a quad.
A triad generally means that all 3 people have relationships with each other, usually emotional and sexual.
I'm in a "V" because I'm involved with 2 people, but they are not involved with each other beyond being friends, so that third side of the triangle isn't present.
Pan Female, Hinge in a V between my mono (straight) husband, Monochrome and my poly (pan) partner, ThatGuyInBlack