So far as I know, it is not prohibited, but in most cases it is a really bad idea. A confirmation sponsor should be someone who can be a spiritual mentor to the candidate, and thus able to call the candidate to spiritual account when needed. Someone in a close personal relationship with the candidate, especially someone who is so intimately involved with the candidate as to be married to that person, generally does not have the necessary objectivity and spiritual freedom to stand against the candidate when challenged on matters of faith and morals.
If your husband cannot find an appropriate sponsor on his own, he should discuss the matter with the RCIA director and/or the pastor. They likely have dealt with the issue before and can assist your husband in finding a qualified sponsor.
