Your relatives may have gotten divorced and listed themselves as widowed on every record after that. Other than the divorce record (if you know where it took place and can find), there may be no mention of how the marriage actually ended.
Census records may give their marital status as widowed, obituaries may mention just the marriage, death certificates may not indicate their marital status as divorced either. Obituaries and death certificates may contain information provided by a relative who did not want others to know of the divorce or may not have actually known about it themselves.
Mention of the court action regarding the divorce in a local newspaper may be one way to potentially find the record.