In a search for their ancestors, more than 140 people with variations of the last name Kincaid have taken DNA tests and shared their results on the Internet.
They have found war heroes, sailors and survivors of the Irish potato famine.
They have also stumbled upon bastards, liars and two-timers.
Much of it is ancient history, long-dead ancestors whose dalliances are part of the intrigue of amateur genealogy. But sometimes the findings strike closer to home.
In one case, two brothers were surprised to discover they had different fathers. They confronted their elderly mother, who denied the most obvious possibilities -- that she had been unfaithful to her husband, the man they had always known as Dad, or that one son was adopted.
"It has been traumatic for some to discover their true lineage through the DNA tests," said Don Kincaid, a 76-year-old Texan who oversees the Kincaid surname project and witnessed the brothers' ordeal.
As genetic testing becomes more widespread for medical information, forensics and ancestral research, more people are accidentally uncovering family secrets. Among the most painful are so-called "non-paternity events," cases in which Dad turns out to be someone else.
"It's going to be more and more of a problem," said Dr. Eric Topol, chief of genomic medicine at Scripps Research Institute in La Jolla. Increasing numbers of people will be asking their spouses and parents: "What happened 25 years ago?"
The direct-to-consumer DNA industry sometimes warns customers of the possibility of unintended consequences. But company involvement stops there.
The two Kincaid brothers declined through a spokesman to talk about their experience, calling it too painful.
Others, with the benefit of genetic distance, are more philosophical.
"I'm sure in the history of the Kinkaide family, there's been some fooling around," said 66-year-old Perry Kinkaide.
"If that's unique to this family, I'd be surprised."
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