After being married for 40 years.. the chances that they have been thru something like this themselves.. is pretty good. Plus parents have that 6th sense.
If they suspect something, I hope it is the 6th sense. I can't ask them about any M problems. If there ever was a OM/OW I would be devastated to hear about it.
I don't know how much of a factor it may be, but it seems that I have a very different outlook on M because the idea that one of my parents will die first and leave the other behind one day tortures me. I can't imagine one without the other. H's parents have been divorced for a long time and he states that they should have D sooner because their M was horrible. We did discuss this before we married. Back then H seemed determined not to repeat his parents mistakes.