From a while back:
One source might not always be correct, but it might not always be incorrect either. Each source containing information needs to be evaluated separately based upon the original intent of the document, the likely informant, probable reliability of the specific information, etc.
A statement in an 1830 probate case indicating that an heir had a child of a certain name is reasonably solid evidence of that parent-child relationship–even if there are no other available documents that make the same statement.
We would still look for additional sources of this relationship, including those that provided either direct or indirect evidence, but would probably not discount it just because no other references to it could be found.