Bonnie Schermer, a novelist in Mishiwaka, Ind., suspected for years that her grandfather kept separate families in North Carolina and the Midwest. Last year, she met Sorenson researchers at a genealogy gathering and they offered to test free of charge genetic samples of Schermer's father and a North Carolina man she thought might be a descendant of her grandfather. Their DNA markers were essentially identical.

Schermer says the news was a shock at first. But now, she says, it gives her a deeper understanding of her past and "more sympathy for our ancestors and their frailties." It also has led her to make friends with her long-lost North Carolina cousins.

In other cases, Sorenson data has disproved theories about family ties. Woodward dealt last year with a Pennsylvania family. The family had grieved for decades about a male relative who wandered away from his parents during a New York City visit as a toddler in 1910, and was never seen again. They speculated he had ended up in an orphanage. If so, the Pennsylvanians thought that a casual acquaintance — the son of a New York orphan — might be their cousin.

The orphan's son closely resembled the Pennsylvanians in appearance. When DNA tests were run, however, it became clear the two families weren't connected. "They were disappointed," Woodward recalled, "but at least they had an answer."

The testing has helped Sorenson make a discovery of his own: One of his distant ancestors probably was a Russian Jewish bookkeeper named Jakob Levinsohn. "I guess I'm a member of the tribe of Levi," he says.