Vietnam veteran Bob Nore submitted a DNA sample to a registry to trace his roots. The registry found Nore had fathered a son whose name is Son Vo, a Los Angeles musician. Nore and Vo have reunited. (YouTube/Son Vo)

Last year, Bob Nore, a Vietnam War veteran in Huntsville, Ala., was working on a family tree and wanted to trace his ancestors’ history and origins. So he sent a vial of saliva and $89 to a DNA registry for analysis.

The results showed British and Nordic stock — no surprises. But then Nore received a message from the registry that floored him: We have found a very high probability of a father-son relationship between you and Son Vo.

“I showed it to my wife, and then I looked him up online and found out that he was born in Vietnam shortly after I left,” said Nore, 67.

He vaguely recalled a brief relationship with a Vietnamese woman in Saigon in 1970, but he remembered little about her and had no idea she was pregnant. Yet he had no doubt that Vo, a 45-year-old musician in Los Angeles, was his son. As an engineer, he said, “I have a lot of trust in DNA.”

Most people who register with DNA databases are looking for information about their ethnic origins or exploring distant branches of the family tree. But the rapidly expanding databases have also had an unintended consequence: They are helping people find biological parents whose identities had long been mysteries.

Moki Evans poses for a portrait in Washington. Evans, a Vietnamese American who was adopted from Vietnam as a baby, is hoping to find her birth father. (Allison Shelley/For The Washington Post)

The implications are wide-reaching. For adoptees, birthparents, children of single mothers with unknown fathers, and fathers unaware that they had a child, the answers to lifelong questions or the revelations of closely guarded secrets may now pop up in inboxes without warning. The technology can raise privacy concerns and lead to emotional complications.

“There’s complex baggage that goes with it,” said Jennifer Utley, a family historian with AncestryDNA, the registry Nore used. The company’s database includes around 2 million people from 30 countries, including thousands seeking birthparents. “All we can say is, ‘You’re going to open up these results, there may be surprises there.’ ”

That may be especially true for adoptees. While some have no interest in seeking out biological relatives, others, particularly older adoptees who grew up in a more secretive era, describe a nagging sense of something unresolved. DNA registries hold out the possibility of closure.

Some adoptees have found biological relatives when they didn’t set out to.

Michael Reed, 61, an adoptee in Mundelein, Ill., had already been rebuffed by a birth mother he had found through traditional means. He signed up with the registry 23andme simply to learn about his ancestry, and he was taken aback when he was matched with a first cousin once removed. Together they figured out that her cousin in Utah was likely Reed’s biological father.

“I was so afraid,” he said. “I’m not what I would call a devout person, but I literally went to my bedroom, dropped to my knees, and prayed that I wouldn’t cause any harm to Dad and his family, that I’d find the right words to say.”

At first, the father, who is 81, thought it was a scam. But when further DNA testing confirmed the match, he invited Reed to Salt Lake City to meet him and his family, which includes nine half-siblings.

Moki Evans shows the passport she was issued in Vietnam as a baby. (Allison Shelley/For The Washington Post)

“They’ve got this huge sign: ‘It’s a Boy!’ ” Reed said of the airport meeting. “It was wonderful to see, but it was overwhelming.”

He has since formed close relationships with his extended paternal family, but he can’t forget how tenuous the original connection was.

“Without the DNA,” he said, choking up, “the miracle would not have been possible.”

It’s harder for families to find an individual adoptee because that specific person would need to sign up, whereas for an adoptee to find a match, anyone related to a birthparent can register and spark a connection. At 23andme, which has around 1 million registrants, participants can opt out of relative matches altogether. AncestryDNA does not have the opt-out option, though both databases allow people to withhold their names and identifying details if they choose to.

Angela Trammel, a genetic genealogist at Kin Finder Group who uses DNA registries to help clients locate relatives, estimates that 25 to 30 percent of birthparents she has contacted don’t want a relationship. But many are willing to share medical information and provide some sense of closure, she said.

“Most of the time they are cordial and some kind of friendship starts to develop — if not with the biological parent, then the biological siblings are often very supportive,” Trammel said.

Lenny Scovel, who was adopted at birth in 1963, grew up as an only child but always sensed he had siblings. His adoption records were sealed, but a couple of years ago his wife gave him a 23andme kit so he could determine his ethnicity.

“I’m sort of poking around the website and I see the DNA relatives tab,” said Scovel, 53, a woodworker, actor and celebrant in Fort Collins, Colo. “There was one woman listed on there as a probable first cousin.”

The woman was not only welcoming, but she had stunning news: The family had been hoping to find him.

Scovel’s sibling hunch was right — he was one of 12 likely children of the same mother, 10 of whom had been placed for adoption. Now in their 50s, 60s and 70s, they lived all over the United States. He wept in his office, watching the flood of Facebook friend requests stream in.

But even when newfound relatives are receptive, the path forward is not always clear.

“Here I am, crowing all over social media, referring to them as brothers and sisters, and a couple of them reminded me gently, ‘Be careful, there are privacy issues here,’ ” he said. “I wasn’t even thinking.”

Such emotional seas can be hard to navigate without a middleman. Trammel said she often makes the first overture to birth families. “I have a client who might be closely related and I ask them if they’re willing to help me,” she said. “It takes the emotion out of it; they can ask questions, they can seek out information.’”

Adoption agencies also provide counseling and function as a buffer between adoptees and birthparents.

In Scovel’s case, the siblings responded with immediate enthusiasm. He learned that only the two oldest had been raised by their mother, who died in 2000. One adoptee had also died, but six had already connected, mostly through adoption advocacy organizations. Last year the seven who are now in touch gathered for the first time; they hope the four remaining ones might eventually register their DNA.

“They are a vial of spit away from finding us,” Scovel said.

The role of DNA registries could also help force the adoption landscape toward further openness.

“With technology what it is, there’s no such thing as confidential adoption any more,” said Janice Goldwater, founder and executive director of Adoptions Together, a Silver Spring-based adoption agency.

Sperm and egg donors who expected to remain anonymous may also see the ground shift.

“It’s rewriting the rules,” said Scott Brown, director of client experience at California Cryobank, which has had 8,000 to 10,000 sperm donors since 1977, resulting in an estimated 60,000 children. The organization used to virtually guarantee anonymity to those requesting it, but it now advises donors about privacy’s limitations.

“We say, ‘Think about what you put on social media, and don’t put the same thing in your [donor] profile. . . . The Internet has changed a lot of things.”

The organization also prefers to facilitate communication between donor-conceived children and their donors rather than letting them connect on their own. “To go through DNA and show up on the doorstep or the family’s doorstep can create a lot of problems and a lot of stress,” Brown said.

Rockville-based Shady Grove Fertility started counseling egg donors this year about the implications of DNA registries. “We advise them that these publicly accessible databases could compromise their anonymity in the future, but that they are protected legally from any responsibility or liability,” said Eric Widra, the center’s medical director. He said few, if any, have decided against donating for that reason.

For those seeking birthparents, reaching out can mean risking rejection. Moki Evans, adopted in 1973 from a Vietnamese orphanage, knows nothing about her biological father, whom she believes was an African American serviceman. After registering with AncestryDNA, the Rockville resident found probable third or fourth cousins in Alabama and Virginia. She sent two messages to the closest match, but he has not responded.

“I don’t know if this family knows about me, wants to know about me, whether they’re indifferent or it’s a nightmare for them,” she said. “I don’t want to hope yet . . . I’m conscious of the fact that I might find some hard truths.”

Son Vo had the same concerns. His mother spirited him out of Vietnam in April 1975 just as the Americans were leaving. Four years after they moved to the United States, she died, leaving no reliable information about his biological father.

A year and a half ago, Vo’s wife gave him an AncestryDNA kit to help him learn about his background. Nine months later, Nore popped up — a match with over 99 percent accuracy.

At first Vo was cautious. “I thought, hey, am I getting punked?” he said. “I have no idea who he is, he could be this raging alcoholic, he could be suffering from PTSD, he could be this angry war veteran.”

But when Vo finally reached out, the two clicked. Nore talked about his guilt about serving in the war; Vo told him about his own narrow escape. Both were musical. Nore sent a ticket for Vo and his wife to come visit. Father and son sang together.

Three weeks later, Vo broke down. “I just sobbed, the happiest dark sob on my wife’s shoulder,” he said. “I let go of years of the unknown . . . and it’s because of DNA, because of the age we live in.”