late edit: DISCLAIMER: The pictured map is not actually a representation of the territories before colonisation. It’s a hypothetical map of what countries there might have been had the continent not been colonised, thus all the names and borders are fictional and have never existed.
For good actual maps, check out native-land.ca.
Somewhat similar: I’ve met at least a dozen people who all claim to somehow be related to al capone most likely because of some rumor started in their family 50 years ago.
People/families like feeling special and unique, a inherited culture is one of the easiest ways to achieve that feeling I guess even if faux.