Spicy hotpot has made the founders of Haidilao restaurant chain one of the wealthiest families on Earth.

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The hotpot couple are reportedly naturalised Singaporeans.

They have a new combined net worth of S$17.9 billion (US$13.2 billion) as of April 12, 2019.

74% jump

According to the Bloomberg Billionaire's Index, Haidilao International Holding chairman Zhang Yong and his wife Shu Ping, who are already billionaires, had further grown S$7.58 billion (US$5.6 billion) richer in 2019.

That's a 74 percent jump in just over three months.

The Bloomberg Billionaire's Index is a ranking of the world's 500 richest people.

Just a month ago in March 2018, Zhang and Shu were already named Singapore's newest billionaires, according to Forbes magazine's list of the world's richest people.

Zhang Yong, 48, was Singapore's third-richest person with a net worth of S$9.2 billion (US$6.8 billion), while his wife, Shu Ping, 49, is ranked 14th with a net worth of S$2.4 billion (US$1.8 billion).

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Started in 1994

Zhang was a former welder at a tractor factory.

The couple started the popular restaurant chain with friends in 1994 and developed a reputation for excellent customer service, allowing it to cut through the clutter of various Chinese hotpot operators.

Little is known about Shu.

She is one of the company's five directors.

She and two other friends helped Zhang financially when he set up his first restaurant with just four tables.

It was in Jianyang, a city in Sichuan province.

Currently, Zhang and Shu have stakes in Haidilao's seasonings and sauce arm, Yihai International Holding.

Yihai International Holding has seen its shares rise more than 87 percent this year.

The couple hold about 58 percent of Haidilao.

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Spending time in Singapore and China

Shu reportedly manages the chain's strategic development.

She lives in Singapore with the couple's son.

Zhang is said to have bought a S$27 million property in Singapore in 2016.

He divides his time between Singapore and China, where there are about 370 outlets.

Went public

Haidilao went public in September 2018.

Shares soared by up to 10.3 percent in early trading on the company's Hong Kong debut.

It had raised nearly US$1 billion in its initial public offering.

There are 11 outlets in Singapore, such as at Clarke Quay, VivoCity and Plaza Singapura.

Haidilao has about 30 outlets outside China, including restaurants in Japan, the United States and South Korea.

Fastest-growing fortunes

Zhang and Shu currently have one of the world's fastest-growing fortunes.

The Chinese husband-and-wife duo are only behind a few other wealthiest individuals in the world.

These include:

- Australian mining baron Andrew Forrest, who has doubled his fortune this year,

- Chinese education tycoon Lu Zhongfang's 83 percent rise, and

- United States used-car billionaire Ernie Garcia's 78 percent gain.

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Rapid expansion

Haidilao is expanding overseas with new locations planned in New York and London.

The company is pushing to make its restaurants more efficient by creating automated kitchens.

In 2018, revenue went up 60 percent to S$14.1 billion (17 billion yuan).

Haidilao International Holding stock has gone up more than 77 percent in 2019 so far.

At S$28.4 billion (US$21 billion), the company's market value is now higher than Chipotle Mexican Grill Inc.

Another billionaire couple

Another power couple behind Haidilao, co-founder and executive director Shi Yonghong and his wife Li Haiyan, have also grown 74 percent wealthier this year, based on Bloomberg's data.

Their fortune is now worth S$8.5 billion (US$6.3 billion).

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