The situation has arisen where a joint pseudonym has been added as an Author credit:
Lewis Padgett which was a joint pseudonym used by husband and wife Henry Kuttner and C. L. Moore.
This is not unique as there are also the Brothers Grimm (both also credited individually) and Erin Hunter which is a house pseudonym used by various authors (some of whom are credited individually).
Personally, I don’t have a problem with this practice but I thought it worthwhile to get opinions on the subject before the numbers increase.