For Rachel Swarns, New York Times reporter and author of "American Tapestry: The Story of the Black, White, and Multiracial Ancestors of Michelle Obama," telling people they are related to the first lady wasn't simple.

"It wasn't easy to say, 'I think a member of your family owned a member of the first lady's family,'" Swarns said. "A lot of us are looking for connections, but that's not usually it."

Swarns was interviewed by Michele Norris, host of NPR's All Things Considered, at the National Archives on Thursday, where the author spent a lot of time researching.

After Swarns published an article in the New York Times in 2009, she was approached by genealogists to trace the first lady's family history. The two-year-long project unearthed surprising finds.

Dolphus Shields, Obama's great-great-grandfather, was biracial. A remarkable photograph shows the Irish-American Shields family, including the first lady's great-great-great-grandfather, a white man wearing spectacles.

A lot of the white families were curious, Swarns said, and "not just because they wanted inauguration tickets."

Swarns doesn't know what the first lady thinks, but she hopes she finds it "fascinating."

- Contributed by Lucy Westcott