From left to right: William Fong; William's paternal grandmother; William's father.

To increase search efficiency and keep prices low, the business relies on a team of field researchers who work on commission. They are mostly young, passionate and have a strong penchant for history.

Deng Shuang, a postgraduate student at a university in Yunnan province in southwest China, is one of them. The 24-year-old's involvement with overseas Chinese looking to learn more about their family history predates his association with My China Roots, which he came across in 2014 while conducting an online search.

"I've been freelancing for a Chinese soccer magazine since 2012, and through interviews I got to know many foreign soccer players of Chinese descent. Some were quite keen to find out about their ancestors' stories," he said.

The players included Kwong-Wah Steinraht, a former professional in the Dutch league, who is a quarter-Chinese. His maternal grandfather followed the same route as Lie's grandparents - from China to Indonesia and then the Netherlands - about 70 years ago. "Steinraht told me that his grandfather actively maintained contact with his relatives in China, until one day he received a letter from home asking him not to write again," Deng said, pointing out that it happened during the height of the "cultural revolution", and the letters may have already brought trouble to his loved ones.

Some searches are bound to come to nothing, not least because China's unprecedented urbanization during the past 20 years has obliterated many reminders of the old days, but for those who discover their family history, the meaning goes far beyond words.