This is not a same-sex wedding specific question, but rather an etiquette question.
My partner and I are getting married in July in Maryland. I found out that one of my college fraternity brothers is going to be in Baltimore on business around the same time (he lives in Boise). I was going to send him an invitation, but I know both he and his wife (we all went to the same college). She is not coming to Baltimore because he will be there on business.
Question: Should the invitation be addressed to just him or to both the husband and wife?
Thanks!