OR, perhaps this unknown spouse is one that was entered by hand, in that case, you can just delete the unknon spouse.
If none of that works, try exporting a GEDCOM file and importing it into a new, empty database and see if the unknown spouse is still there.
I tried everything except selecting delete family. Program wouldn't let me delete the unknown spouse but when I selected delete family, I was able to at least unlink the unknown spouse. It is now gone. Thanks!