Some secrets are difficult to uncover, especially if you have no inkling that they ever happened in the first place. If you do not ask, no one will volunteer the information. Sometimes if you ask, they still will not provide any information or say that the event never took place. And sometimes you do not even know specifically what to ask and the only “clue” you have is an inkling that there’s something you are not being told about a certain family member (and…your “gut” could be wrong). And it could be that there’s a “secret” about a family member that only a few other family members are even aware of and they have an unwritten pact among themselves not to tell anyone else.
If a great-uncle lived in Kansas for two years and returned home to Illinois, don’t assume that nothing happened in Kansas. He could have been in jail, gotten married/divorced, had a child no one talked about, or lived a mundane life that only generated bills and rent receipts.
Never assume that Grandma is telling you “everything.” Even if she is telling everything she knows, someone else may have held some details from her. Just because the facts Grandma told you are correct, does not mean that she’s told you everything she knows.
She may just hope you don’t find out that her brother was married in 1920 and divorced three months later. Or no one may have told her that her own father’s brother had a first wife with whom he had three children.