OK - a really hard one which I will try and keep in non-identifiable bullet points since it involves someone else's relationship:
- good friend, male, has been in relationship for a significant number of years, no children
- relationship seemed to be going well
- out of the blue, wife announces that she has (allegedly unconsummated) feelings for colleague/friend
- complete shock but both parties say they want it to work
- fall out involves discussion with another friend, who then confides to my DH that a year to 18 months ago, his girlfriend accidentally picked up the wife's phone at a lunch function (same kind of phone) and read a sexually explicit message between the wife and the colleague/friend concerned - not mentioned at the time. He has now passed this on to DH.
Should DH tell our friend? Which would be likely to be the kiss of death on the relationship? Or wait until friend and wife have finished counselling, and see whether it comes up? Or what? Every alternative seems to have a downside.