Best of Luck Rebecca. In cases like that, you might have to rely on documents such as marriage certificates, newspapers, etc to prove to them they are mistaken.
Maybe if you had all that, and wrote them with copies? But, some people can have proof in front of them and still won't budge. I agree, very frustrating when they are sitting on info we want/need.
As I have done research, I have come across some very deep family secrets. Some I can understand keeping quiet, others that while I don't think are that big of a deal, to them it is very private.
Good Luck and keep us informed.
Tina