Kris Chung was a 19-year-old student at the Royal Military College in Kingston, Ont., when he decided to donate part of his liver to a total stranger. The recipient? A young girl suffering from a rare disorder that was attacking her liver.

Binh and Phuoc Wagner's story made international headlines last year.

A couple from Kingston adopted the twin girls from Vietnam when they were 18 months old. Both have Alagille syndrome, a disorder that affects internal organs.

The girls' father, Michael, was a genetic match — but he could only donate part of his liver to one of his then-three-year-old daughters. Doctors decided which of the twins would receive the liver transplant from their father after the family said it could not make the heart-wrenching decision.

Johanne Wagner says Kris Chung, pictured here, now calls her daughter 'my Binh.' (Facebook/Kris Chung)

After Michael and Phuoc underwent a successful liver transplant in February 2015, the Wagners turned to the public for help in finding a donor for Binh. They put a call out for donors between 18 and 55 years old with A or O blood type, posting photos of the girls and their family.

One of those photos stuck out for Chung: one of Michael, flanked by several of his nine children, wearing his military uniform. "I think it's instinctive for military members to help one another out," Chung said.

He found out he was a match for Binh and filled out the application forms that same day.

Nearly 500 people contacted Toronto General Hospital to offer parts of their livers to Binh. Chung was actually second on the list of donors, and wasn't sure he'd even have to go through with the procedure.

Then, in April, he received a phone call. The first donor had backed out.

​"There was pretty much a 12-hour notice," Chung said.

He got permission to leave campus, booked a train ticket to Toronto, and left within a couple of hours.

Binh Wagner holds hands with the man who donated part of his liver to her. (Facebook/Liver Transplants for our Vietnamese Twin Girls)

'You get to save a life'

Chung says he kept the whole thing quiet to focus on his recovery, as well as his schoolwork. Falling behind in classes would have meant graduating a year later than scheduled.

His brother knew about the transplant because Chung gave him power of attorney in case of complications during surgery. He didn't tell his parents, who live in Vancouver, until two weeks after the procedure.

"I thought that they would try to stop me," he said with a laugh. "But I knew it was something I had to do, and that it would turn out to be successful."

Thanks to his professors, Chung says he was able to postpone his exams until the summer so had time to recover. He was on bed rest for about a month, and it took four months until he was able to do any kind of physical activity.

Now, more than a year later, he says he's fully recovered and appears to have been fully accepted into the Wagner family.

The mother of Binh and Phuoc Wagner says the twins are doing well. (Twins for Hope/GoFundMe)

'Just like meeting an old friend'

The girls' mother, Johanne Wagner, says she thought a lot about the anonymous donor on the morning Binh received her liver transplant. The mystery of who that person was, however, didn't last long.

About two weeks after the surgery, she received an anonymous tip identifying Chung.

"I remember feeling so, so angry," Wagner said. "'Who are you, and what gives you the right, to break this person's desire to remain anonymous?'"

She didn't reach out to Chung in an effort to respect his wishes. But for nearly a year, while she updated the girls' Facebook page with photos and news of their recovery, Wagner noticed Chung was paying attention, liking their photos and commenting on them.

"I was so uplifted when I would see that he liked a comment or made a comment, thinking, 'OK, you're still there. You're still out there, watching out for Binh.'"

Eventually the pair struck up a conversation about Chung's Cantonese background, which later turned into long emails about shared values and beliefs. But neither mentioned their connection to Binh.

Finally, he asked if he could meet the couple. Johanne says she was ecstatic and finally told Chung they knew he was the donor.

"We chatted for hours," she said. "It was just like meeting an old friend — somebody I hadn't seen for so long."

A week-and-a-half later, Chung met the little girl whose life he saved.

"She was a little bit nervous, but not too long after, she came over and gave me a good hug," Chung said.

"I used to cuddle with Binh and I used to get teary-eyed thinking, 'Wow,'" Johanne said. "'I'm about two inches away from him but he's not in my house.' So watching him and Binh is fabulous."

Paying it forward

Johanne says her family couldn't have been any luckier with the outcome of her daughters' transplants. Both girls are doing well and have gained important people in their lives, she said.

"As far as I'm concerned, it's not just Kris who joined our family. It's his family unit that merged with ours."

Twins for Hope was founded in honour of Binh and Phuoc Wagner. (Twins for Hope/GoFundMe)

The pair has now founded a charity called Twins for Hope in Phuoc and Binh's honour. They're aiming to raise $25,000 by December on GoFundMe to help impoverished children in the twins' birthplace of Vietnam.

The money will go toward everything from medical care and community programs, to things like bicycles to help children get to school safely.

"This endeavour that I took on is only a short one," Chung said of his effort to help save a young girl's life. "I'd like to continue that throughout my life."