Unable to add husband to Family Sharing account

I have a family account set up to provide back-up storage. 3 people had no problem joining the family. My husband is unable to join. I send him an invitation via email or text. He tries to accept it. But he gets a message that he's already a member of the family. The Apple store was unable to help. I had a phone call and the support person was supposed to get back to me but never did. How can I get my husband added to the family?

Or, can I cancel/close the family -- and then start a new one?

[Re-Titled by Moderator]