On a weekend night in Washington in the U.S., he is teaching a Vietnamese-American drive a car. He is one of the wartime children Tung helped find his biological father in the U.S.

Tung, 52, a quality controller at an airport, is touched every time he witnesses a reunion between a person and their American parent. He knows how it feels to be in the former’s shoes since he has himself experienced that joy after losing contact with his American father for 25 years.

Tung was born in Saigon and raised by his Vietnamese mother, Phan Kim Chi. His father, James A. Miller, was an American soldier who married Chi in 1966. But a year later Miller was injured and returned to his country.

Since her husband left without any contact details, Chi believed he had abandoned her and her son. 

In the fog of war, she chose to bury her past and moved on to have a new family. Miller sent many letters to his family, but she hid them away.

But for Tung, childhood, growing up without knowing his father, was a nightmare. It fueled a burning desire in him to find his father. 

But even after migrating to the U.S., his efforts to track down for his father were fruitless for 25 long years. 

One day his cousin found a seal on an old letter from his father, managed to find out from which post office it was sent, and eventually managed to contact Tung's father. 

Tung remembers his first call and first meeting with his father when all the bitterness and misery of his childhood just seemed to melt away.

The 25-year separation from his father had left a scar in his heart, and he had thought he was the only such unfortunate one. A documentary he saw in 2007 revealed to him his mistake: Many others were in the same situation having lost contact with their parents. Many had to bury the longing to find their family due to various personal issues.

"I thought I needed to connect with these people and help them," Tung says. 

He tried to contact Vietnamese-American friends around Vietnam. In 2009 he founded a non-profit called Tinh lai khong bien gioi (Amerasians Without Borders). It has so far offered free DNA testing for more than 400 people living in Vietnam and helped dozens of U.S. soldiers reunite with their children.

On many nights Tung has sat at his computer, looking up DNA data to help a friend in Vietnam or telling a person in the U.S. how to find their father, his mother says.

Most of the American fathers have been willing to meet their children, but there has been the odd case where they wanted to forget the past.

"Tell him to stay in Vietnam," some have told Tung refusing to connect with their child, not wanting to revisit their sins in the past.

Tung would then start to coax them. "I would explain to them that the war has ended and Vietnamese no longer see American soldiers as enemies.

"The children are only eager to know their origin. 

"And they would finally reach out to their children."