Julian Arnold was the U.S. commercial attache to China in 1936, when he gave a talk about the virtues of the soybean.

He called it “The Cow of China,” explaining that the legume packed just as much nutrition as milk. The speech so inspired Lo Kwee-seong that he founded his own soy milk company four years later in Hong Kong, billing it as a nutritional supplement because the working class couldn’t afford milk during war time.

Today, Vitasoy International Holdings Ltd. sells its products in 40 markets, from the U.S. to Australia, with mainland China accounting for more than half of its revenue.

Shares of the soy milk maker have surged more than 3,500% since the company’s 1994 initial public offering, and eight members of the Lo family are reaping the rewards. They’re worth a combined $1.5 billion, according to the Bloomberg Billionaires Index.