How would anyone know if I told my wife something I should t have? If they’d ask me, I’d simply say, “No.”
If they say, “Can I talk to you in confidence?” and you say “yes”, rather than “well, yes, except there is essentially nothing I never tell Sally, but she’ll never tell” and then you go off and tell your wife the things that you said you wouldn’t tell anyone, you have lied to the friend who asked for confidentiality. Maybe nobody ever knows that you lied, but you did.
If, however, “except that there is essentially nothing I never tell Sally” is a universal expectation that is well-known, then “confidential” allows you to tell your wife unless it is particularly established that even she may not be told.
Incidentally, I have experience with just such a confidence being violated. One in-law talked to a family member with the assurance of confidentiality, that family member told his sibling–because how could the 1st in-law mean I wouldn’t tell my brother?–the brother who was told blew a gasket, the in-law who expected confidentiality was mortified and angry, and a lot of people quit speaking to each other for several years. Do they ever confide in each other now? Yeah, right…
that’s not going to happen! May as well just send out a group e-mail!
I know another family in which one brother kept some confidential papers for the parents, due to the parents’ incapacitation. He insisted that he could tell no one about these confidential matters. This was all great until his wife accidentally spilled some information that the brother with the confidential knowledge had told her. When the siblings found out that this information was being withheld from them but that their SIL was being let in on it, there was an uproar. How could
their parents’ information be* her *business and not
theirs?
Asking for in-family confidentiality has its risks, but since the OP asked for permission to tell her husband and it was not given, she would be very wise to keep her mouth shut at least until she has given the in-law who confided in her warning that she was going to let her husband in on the secrets. If the confiding in-law is the last person to find out that her confidence has been breached–and are you really expecting a man to not tell his own brother about information he has on that brother’s wife that his brother does not have?–I expect she will be very upset…and I do mean VERY upset.
OP, you’ve asked for permission and not gotten it. Do not divulge anything to anyone at least until you’ve told the confiding in-law that you’re going to tell your husband. If you tell without giving her a heads-up, you may start a chain reaction that you really do not want to start. Once it is done, you cannot un-do it. All bets are off if someone is in danger, but otherwise, don’t tell.