Steeped in romantic folklore, the Broken Bridge in Hangzhou, China is a major tourist attraction that draws tens of millions of visitors each year to the shores of West Lake.

Since 2004, a man named Xu Lida braves the throngs to return to the bridge every year on the same day. But he is no ordinary tourist taking in the sights. Arriving early in the morning and staying until late in the afternoon, Lida scans the faces in the crowd, hoping to see a strange, yet familiar face-the one of the daughter lost so long ago.

Since China began international adoptions in the early 1990s, adoptive parents have little information about their child's birth family. Birth parents in China often leave no identifying information and disappear without a trace after relinquishing their children. The lack of knowledge about their origins leaves many adoptees with a void that leads to the desire to find their roots, especially as they come of age and grapple with their identity.

But birth parents searches in China are difficult at best and with so few found to date, there is little advice for dealing with the emotional complexity surrounding the rare times a birth family is found. The Xu and Pohler families know these emotional complexities because they have lived with it for the past 20 years.

Lida and his wife Fenxiang told the BBC that after marrying in 1992 and welcoming their first daughter, they decided to have another child so that their eldest child wouldn't be lonely without a sibling.

But giving their eldest a sibling would violate the one-child policy, a measure introduced by the Chinese government in 1979 to control its soaring population growth. Disobeying this rule resulted in harsh punishments, including steep fines, loss of property, forced abortion and sterilization.

When Fenxiang's pregnancy was discovered in her fifth month, family planning officials demanded an abortion and threatened to tear down their home. But according to Fenxiang, "The baby's life was already formed. I couldn't abort it."

So Lida and Fenxiang decided to start a life on the run to give birth to their child, even if it meant giving her to someone else.

They hid on a boat on the river where Fenxiang gave birth to their daughter. Three days later, Lida took their baby to a vegetable market where he kissed the sleeping baby gently as he knew it was farewell. But he didn't just leave her with a kiss--he also left a note.

A year later, Michigan couple Ruth and Ken Pohler adopted their daughter Kati from the Suzhou Social Welfare Institute. Ruth still gets emotional when she remembers the moment that they handed her daughter to her.

Kati's adoptive parents the Pohlers.Photo: BBC

Along with their daughter, the Pohlers also received an unexpected piece of paper written by Kati's birth parents. The note ended with a passionate plea: "If God has sympathy for us and you care about us, let's meet on the Broken Bridge on the West Lake in Hangzhou on the morning of Chinese lunar date July 7th in 10 or 20 years."

Similar to Valentine's Day, the date of Lunar July 7th is a special day in China, a day for loved ones to meet and reunite.

The Pohlers thought little of the note as they settled into family life, but ten years after they adopted Kati, they found a messenger through a friend and sent her to the bridge on the appointed day as requested in the note.

The messenger found the birth parents after the story became news in China and captivated a national audience. Lida and Fenxiang were thrilled to receive news of their younger daughter and began to plan for a reunion. But after the messenger became reluctant to continue and disappeared, their connection was lost.

While the birth family was happy for the connection, the Pohlers were overwhelmed when faced with something that most in the Chinese adoption community were told was impossible. Ken was "stunned" and Ruth was "petrified" as they grappled for the first time with the reality of sharing their daughter with someone else. After much thought, they decided to wait to share the information with Kati, but let the birth parents know that she was well cared for and deeply loved by her adoptive parents.

Lida and Fenxiang continued to make their annual trek to the bridge on Lunar July 7th. Knowing that they were connected to their daughter who was alive and well in the United States gave them hope every year that this would be the year they would be reunited, only to be disappointed again. As they wondered why they waited, they feared that their daughter held a grudge or that they were being punished by God, which they felt they deserved.

Kati reunited with her birth parents.Photo: BBC

The Pohlers decided to wait for Kati to express a desire to know more about her birth family before sharing what they knew. They struggled with their knowledge as the years passed until Kati finally asked the right questions of them when she was 20.

After her adoptive parents told her what they knew, Kati questioned why they waited so long to tell her. Ken and Ruth told the BBC they have regrets, even though they feel they made the best decision at the time. The secrets and regrets have strained Kati's relationship with her parents.

Photo: BBC

Kati decided to go to the bridge in China to meet her birth parents on the appointed day. Ken and Ruth offered to go with her to China, but Kati declined. While one set of parents wait in the place she has always called home, Kati is going to that bridge in Hangzhou to meet another set of parents who wait for her in the home left long ago, starting a new chapter of her story.

See what happens when Kati meets her family on BBC Stories, Meet Me On The Bridge - on the BBC News website now. Or watch BBC Our World on BBC World News, Starhub channel 701.