Cheng Yu-tung, who helped develop the Chow Tai Fook jewelry chain, the world's largest jewelry retailer, and went on to become one of Hong Kong's billionaires, has died. He was 91.

Cheng died peacefully with his family at his side Thursday night, his family said in an e-mailed statement.

Besides Chow Tai Fook, Cheng was chairman of New World Development. In February 2012, he announced his retirement as chairman of the company, which was founded in 1970 and operates in businesses including energy, bus services, department stores and real estate, which includes New York's Carlyle Hotel.

Henry Cheng Kar-shun, the eldest son of Cheng Yu-tung, said on Friday evening that his father had been in a coma since he underwent brain surgery four years ago. His death will not affect New World Development's operation, he added.

Like fellow billionaire Li Ka-shing, Cheng was among Chinese refugees who fled from Japanese invaders and made it big outside of the mainland. Cheng, the third-richest tycoon in the city on the Bloomberg Billionaires Index, had an estimated net worth of $12.7 billion through his holdings in Chow Tai Fook Jewellery Group Ltd and New World Development Co.

Cheng was honorary chairman of Chow Tai Fook Jewellery, which operates more than 2,000 outlets in China and Hong Kong, and whose revenue was more than 70 percent larger than that of New York-based Tiffany & Co in the latest fiscal year. The jewelry-chain operator has struggled recently in Hong Kong as mainland Chinese tourists skip the shopping mecca for other destinations.

Profit for the year ended March 31 fell by 46 percent, slumping to the lowest since 2010. The chain is now looking to new strategies such as operating art galleries merged with malls in China, and selling diamonds wholesale to U.S. retailers to diversify away from its retail business.

As his businesses took off, he would visit jewelry stores unannounced to check on them, and eat with his workers at the company canteen. He wore Nike running shoes with business suits.

Cheng was born on Aug 26, 1925, in Shunde, a city in Guangdong, the southern Chinese province adjoining Hong Kong. In 1940, he fled to Macau to escape China's war with Japan.

At the age of 15, Cheng got his first job as an apprentice at the gold shop of family friend Chow Chi Yeun, who had founded Chow Tai Fook in 1929. Three years later, Cheng married Chow's daughter, Tsui Ying, in a marriage arranged by their fathers.

In 1946, Cheng moved to Hong Kong from Macau to open a store. The jewelry chain expanded as Hong Kong's population doubled to almost 1.5 million with mostly displaced refugees. By 1950, the city's population swelled to more than 2 million as Chinese fled Communist China, and Cheng used the profits from selling gold to fund his property purchases.

Cheng was a major philanthropist in Hong Kong. In April 2012, he spoke at a groundbreaking for a building that was named after him at the Hong Kong University of Science and Technology.

Cheng took Chow Tai Fook public in December 2011, raising $2 billion in a Hong Kong share sale. Two months later, he announced his retirement from that business.

Last December, Cheng transferred some of his stock holdings to family funds and agreed to sell $3.2 billion of Chinese property projects in a move seen as an effort to put his affairs in order.

Cheng and his wife had two sons, Henry Cheng and Peter Cheng, and two daughters, Amy Cheng and Cheng Lai Ha.