were they legally married before and just didn't have their certificate?
Common law marriage... they never had a certificate and never needed one previously... not for their mortgage, car loans, IRS, local taxes, or anything.
After going to a justice of the peace in VA (they live in PA) they went to Pittsburgh and had a little ceremony in the presence of a couple of close friends. I told them "it's about time you kids got married!"
It was easier for them to do in VA than in PA, because the PA application for the certificate of marriage requires them to certify that they're not currently married, and they weren't going to do that. Apparently the VA application leaves out that minor detail.