Why would they have to be married? What evidence is there to assume this? I suppose if you feel, as many do, that the sexual act is “marriage” then they are married. However, I do not believe there was a ceremony or official event to say “you are now wed”. To me, that is a creation of man, while the concept is a creation of God.
Anyway, this is not the point. The point is that what is obvious to you, cannot be assumed to be obvious to others.