When Linda Ketchum of Glendale, Calif., asked her husband for an AncestryDNA kit for Christmas, it was just a lark. She had no family secrets she was trying to uncover, no genealogy mysteries that needed answers. She was just curious.

“My dad was German, and my mother was Scottish-English,” she says. “I thought it’d be fun to learn a little about my genetic ethnicity, to trace how all the pieces came together.” But she ended up getting far more than she bargained for.

When she went on the AncestryDNA site to view her DNA matches, there were no connections between her and her father. Even more unsettling, at least two-thirds of Ketchum’s matches had Hispanic surnames. “At first I didn’t believe it,” she says. “But then I kept re-checking it, and I realized, oh my God, does this mean I’m . . . I’m Hispanic! All these years I thought I was German on my dad’s side, but all of a sudden it was dawning on me that my dad wasn’t my real dad and I had an entirely different ethnicity.”