Shortly after the Forbes family sold control of its magazine and publishing business in 2014, Tim Forbes held a meeting in Hong Kong with one of the new owners. Mr. Forbes, younger brother of Steve Forbes, had been trying for weeks to collect an interest payment from the buyers. But in the October meeting, Mr. Forbes said his family had waited long enough for the $46,000 payment. The refusal to pay, he said, was “a disrespect to my family and disrespect to me personally.”

The fight over a mere five figures has since exploded into an all-out war over the future of Forbes Media and the reputations of the Forbes family as well as the Asian tycoons who bought the company for $415 million. In a strange twist, the buyer and seller of Forbes magazine, famous for listing the world’s wealthiest people, have accused each other of being short on cash.

The Forbes family says that because of the missed interest payment, a loan of $65 million it made to the buyers is now in default. It wants the entire amount of the loan, as well as $35 million that was set aside in case of any breaches of the sales contract, bringing the total claim to over $100 million. If the family doesn’t get paid, it says, it will liquidate Forbes Media’s new parent company, which could force another sale of Forbes Media.

Both sides say the dispute hasn’t affected the daily operations of Forbes Media, which showed a revenue increase of 15 percent last year over the previous year. But some employees say it’s another potential distraction less than two years after the company was sold.

Forbes’s new owners, operating under a company called Integrated Whale Media Investments, say the lawsuit is without merit and that the Forbes family breached the sales contract by failing to disclose costly legal claims against the company. Integrated Whale says in court documents that it sweetened its purchase of the company to “accommodate the Forbes family’s personal financial reasons.” In a statement, the family said that it “has plenty of cash and no debt, unlike Integrated Whale, which defaulted on its debts to the family only a few weeks after the deal closed.”

The Forbes family has sold off many of its trophies, including its collection of Fabergé eggs; its New York City headquarters building; a Fijian island; its 151-foot yacht, called Highlander (along with the matching helicopter displaying the motto: “The Capitalist Tool”); an art collection; and a 17th-century house in London. The Forbes crown jewel — Forbes Media, which includes Forbes magazine, the website and other properties — was chopped up in 2006. Forty-five percent of it was sold to Elevation Partners, a private equity firm, for about $230 million. In 2014, Elevation and the Forbes family started shopping the whole company to possible buyers.

Integrated Whale ended up as the winning bidder. Little is known about the company, other than the names of three of its principals: Yam Tak Cheung, known as TC Yam; Wong Siu Wa, known as Sammy Wong; and Wayne Hsieh. Mr. Yam is said to be a Hong Kong businessman who invests in private and public companies. Mr. Wong often acts as Mr. Yam’s go-between. Mr. Hsieh, a co-founder of Asustek Computer, a Singapore-based computer hardware maker, is not as directly involved in Forbes Media.

Under terms of the deal, Integrated Whale bought 95 percent of the company, and the Forbes family retained 5 percent, along with board seats and certain rights. Of the $415.6 million purchase price, $350 million was in cash and $65.6 million was structured as a loan, meant to give the Forbes family tax benefits. The first interest payment of $46,459 was due Oct. 1, 2014. Integrated Whale said the missed interest payment was because of “internal logistical errors,” according to court filings.

On Oct. 10, Tim Forbes sent an email to Mr. Wong reminding him that the money was 10 days past due.

“I know we all agree that it is important that we get off to a harmonious start to our relationship,” Mr. Forbes wrote. “Please let me know when we can expect payment of what we are due.”

Integrated Whale paid the interest on Nov. 18. But the Forbes family claimed the delay caused a default of the loan and that Integrated Whale owes it the entire $65 million. The dispute first landed in court in the British Virgin Islands, where Integrated Whale is registered. Last October the Forbes family, through its investment vehicle Highland Management L.L.C., sued in Chancery Court in Delaware.

The payment dispute has quickly become ugly. Integrated Whale has begun “a retaliatory, multifront campaign of oppression” against the family, according to court filings by the Forbes family. In its own court filings, Integrated Whale is seeking to hold on to the escrow, in part because of what it calls a “commercial bribery claim” involving Forbes Media’s operations in Ukraine.

When the deal was announced, the Forbes family praised the new buyers as “a forward-looking investor group” that respects “our brand and our values.” Now it has a different view. In a statement, the family said Integrated Whale’s actions “have only confirmed and deepened grievous doubts as to its intent and its ability to fulfill its contractual obligations.”