Stewart Horejsi’s business was in a funk. It was 1980, and Brown Welding Supply LLC, his family’s third-generation distributor of hydrogen and oxygen tanks, was battling competitors that were intent on expanding into the corner of Kansas he controlled.

“It was a profitable business, but companies took their money and bought more trucks,” Horejsi, 75, said in a telephone interview from his home in Paradise Valley, Arizona. “The competition just grew.”

Frustrated, Horejsi bought 40 shares of Berkshire Hathaway Inc. for $265 each with the company’s cash after friends told him about Warren Buffett, the company’s then-little known chairman. He bought another 60 shares two weeks later at $295 and 200 more at $330 a month after that.

Today, he’s a billionaire. The 4,300 Class A shares of the Omaha, Nebraska-based conglomerate Horejsi says he holds is bigger than the stake controlled by Bill Gates, 57, the world’s richest person and Buffett’s bridge partner. His stake was valued at $742 million at 9:35 a.m. in New York. He has a net worth of at least $1.1 billion, according to the Bloomberg Billionaires Index, and has never appeared on an international wealth ranking.

Horejsi joins a squad of billionaires minted by Berkshire. In addition to Buffett, the world’s fourth-richest person, at least six current or former billionaires derive their fortunes from Berkshire. They include Charles Munger, 89, the company’s vice chairman and David Gottesman, 86, a Berkshire board member and founder of asset management firm First Manhattan Co.

‘Folding Chairs’

Buffett’s late wife, Susan, died in 2004 with a 2.2 percent economic interest in Berkshire. Albert Ueltschi, founder of FlightSafety International Inc., which Berkshire acquired in 1996 for about $1.5 billion in stock and cash, sold his 31.8 percent stake for Berkshire shares, a holding that would have been valued at $2.4 billion when he died 16 years later. Harold Alfond, founder of the Dexter Shoe Co., died in 2007 with $3 billion in Berkshire stock.

There are probably other Berkshire billionaires to be uncovered. In a June 2010 Fortune magazine article, Buffett said that he knew of two Berkshire shareholders who qualify for the Forbes 400 list of wealthiest Americans, and weren’t on it.

“There are a lot of them out there,” Debra Bosanek, Buffett’s assistant, said in an e-mail, referring to the number of people who could have become Berkshire billionaires had they not given their shares to charity. She said Buffett, 83, declined to comment.

‘Better Value’