If I were you, I would record this couple as a "probable", noting them as such in your records. I have one or two instances like that myself, where there does not seem to be any alternatives, and I record them accordingly, with a big caveat in the notes.
To paraphrase Sherlock Holmes, "When you have ruled out everything else, whatever is left, however unlikely, is the correct one".
But because we, as genealogists, require proof, you need to record any cases like this with a flag, or a sticky note etc.
Darren
