I had a relative who wrote a memoir that extended from his childhood through his mid-thirties. It was a mixture of his personal experiences with some remembrances of family members thrown in.
The problem was that, for one reason or another known only to himself, he ended up fictionalizing in several places. It is difficult to know where the truth ends and creative writing begins.
It is like that with some family stories as well. Fiction gets added to make an ancestor sound a little more adventurous than she was. Your aunt thinks her life was dull so she adds a romantic adventure–complete with husband–that never took place. Your uncle’s memory begins to fade as he ages.
Always write down the story as it was told to you–including who told it and the date. Then go from there to determine what aspects of the story may have generated records.