Mr. Luu had his DNA tested, and it was a match. In November, Mr. Magee, a retired teacher from Southern California, visited Mr. Luu on his birthday. An awkward relationship, full of possibility but not untouched by resentment and wariness, was born.

Mr. Magee now calls his son weekly, checking to make sure he is still working in his job cleaning hospital rooms in Baltimore. He also shipped a used Toyota Corolla from California to Mr. Luu, who had been commuting by bus.

“I was stunned he was out there,” Mr. Magee, 75, said in an interview.

Now that he has found his father, Mr. Luu said, he feels stronger. But the discovery, he has realized, has not solved his problems. What can a former felon do to make a better living? Go to college? Start a business? Drug dealing remains a powerful temptation.

“I just wish I had met him before,” Mr. Luu said. “He could have taught me things.”

Brian Hjort, a Danish man who has helped Mr. Luu and other Vietnamese track down their fathers, says Amerasians often have unrealistically high expectations for reunions with fathers, hoping they will heal deep emotional wounds. But the veterans they meet are often infirm or struggling economically. Sometimes the relationships are emotionally unfulfilling.

“I try to tell them: I can’t guarantee love,” Mr. Hjort said. “I can only try to find your father.”

Mr. Hjort, 42, is among a small coterie of self-trained experts who have helped Amerasians track down fathers, mostly pro bono. An industrial painter from Copenhagen, he first met Amerasians while traveling through Vietnam and the Philippines two decades ago and was struck by their desperate poverty.

One asked him to find a friend’s father, and to his amazement he tracked the man down even though he had no knowledge of military records. News of Mr. Hjort’s success traveled rapidly through Amerasian circles, and he was soon besieged with pleas for help. Moved by the Amerasians’ suffering, he took on more cases, charging only the cost of his trips to Vietnam. He created a Web site, fatherfounded.org, that brought more requests than he could handle.

Working in his spare time, he has found scores of fathers, he estimates. Some had died, and many others hung up on him. A few have threatened to sue him. But perhaps two dozen have accepted their children. And in recent years, veterans, too, have begun asking for help. James Copeland was one.