Rebekah Lloyd, 53, of Denver wrestles with her conscience as she plots to visit an 86-year-old aunt, who has dementia. "I feel a little like a DNA vampire," Lloyd said. But her aunt's cells, Lloyd believes, may hold crucial confirmation of her own American Indian ancestry.

Bob Grieve, 55, stores a DNA kit in his refrigerator to use upon his father's death.

After testing his own DNA at the request of a distant cousin, Grieve was shaken to discover that he did not match any of his extended family, including his first cousin, the son of his father's brother.

That could only mean an occurrence of what genetic genealogists call a "nonpaternal event." Either his father was not his father, or his grandfather was not his father's father. But the elder Grieve has refused to surrender to the swab.

"I don't put blame on anybody," saidGrieve, an engine design checker in Dearborn, Mich. "It would just be nice to know where I came from."

Roberta Estes, for her part, is contemplating exhumation. After three decades researching the Estes family tree, and recruiting 70 Esteses for DNA testing, Estes found reason to question whether her father was, in fact, an Estes.

He has been dead for 43 years.

Estes, a technology consultant in Brighton, Mich., recently got a $20,000 estimate for digging him up.