As a genealogy beginner, I was thrown for a while by recorded family lore that a German line from a small village near Freiburg called "Wellinger" was actually linked to a cousin of the Duke of Wellington, who lived his life in a castle on the Rhine and married a German princess in the 1700's.
On the one hand I wanted to laugh right away at this trumped-up story. On the other, so far, most of the improbable "family stories" I had researched had turned out to be basically true.
My great-grandmother, supposedly niece to this Germanized noble, was--so far as I could learn--descended from stone masons and butchers for about 200 years in that same small village. Her greatest adventure was crossing the Atlantic Ocean with her sister to escape starvation, to find her future in a new land.
The one who recorded the story was misled, I think, by this woman's daughter, a true romantic in a German-hating world (about 1930), who wove herself a new past--out of her knowledge of English history. And passed it on without concern to the first family genealogist (my aunt), who dutifully placed it in her archives.
I checked the genealogy of the Duke of Wellington rather carefully online and began to doubt. When I later confirmed more of the family's roots by a visit to Germany myself, I gave up entirely on this hopeless dead-end.
And still I added it as a footnote to Great Grandmother's family history as something, according to the second family genealogist (myself), very unlikely but not definitely disproved.