Race/Ethnicity Question. What to do if you come about new but unverifiable information?

I think you should mark that all your races, including Native American.

This is a very interesting story and could make for a compelling essay if (and I mean that as a very big “if”) you can write it in a way that it’s about you, the applicant, rather than your grandfather. Maybe about the process of learning the story, becoming curious about your heritage, researching, etc.