Just explain if the relationship was known by family or friends. If they never met in person, that is exactly what you have to explain. Why didn't they meet in person? Explain the circumstances. Also, if they met him on skype I would consider that a first meeting. In my case neither my husband has met my family in person nor I met his, however, we explained the circumstances in detail. Since your husband hasn't met your family in person, explain other ways that he has had the opportunity to get to know them. Did your husband meet them on skype? talk on the phone? If so you can explain that. In my case, I met my husbands family on skype, so I explained that to be the first meeting and also added screen shots of our video calls.
I hope this helps... let me know if you have any other questions. Your case seems similar to mine