Most adult choirs contain at least one couple, and some several more. This is usually a positive thing, but there are certain situations where it can be a liability in some ways:
a) the conductor’s partner who does the choir admin. This is sometimes a way for a conductor to keep tight control of the choir while appearing to relinquish some of it. I remember telephoning the membership secretary of a choir whose conductor was dragging his feet about auditions, and leaving a message, only to learn later that I’d left the message with the conductor, who probably never passed it on. A further problem can arise when the couple who between them run the choir split up.
b) the weaker half. It can happen that a singer who would not otherwise make it into the choir is admitted as a way of securing the services of their partner. (I know of no cases of this in any choir I currently sing with, however.) I once toured with a well-known choir (it broadcasts) whose soprano section seemed to be largely made up of such people, which was hard work for the others!
c) the social black holes. We’ve all met them – the couples who talk only to one another. If anyone makes the mistake of trying to talk one of them, they turn to the other and murmur something quietly. Best thing to do is to note which ones they are and ignore them too.