The founder of a medical-supply company in the San Fernando Valley had built her business into a $30 million enterprise. Her two sons felt it was time for mom to move aside and they didn’t appreciate her decision to linger on.

The dispute split the family in two to the point where the sons refused to have Thanksgiving dinner with their mother. The founder, who did not feel her sons were ready to take over but also did not want to fire them, instead put the company up for sale.

“She was ready to just give away the business,” said John Rooney, president of the Valley Economic Development Center Inc., which consulted the company. “To her, it wasn’t worth losing the love of her children to have a successful business and that’s what it came down to.”

Such problems come with the territory of family-owned and family-controlled businesses whether they are small, private firms or giant corporations. While few of the problems are unique to family-owned businesses, they often are exacerbated because family roles and business roles often become confused.

In the case of the medical-supply firm, the sons, not wanting to see the company sold, agreed to work with their mother and write a detailed business plan, including milestones to be reached prior to succession.

But not all disagreements end harmoniously. Many lead to years-long estrangements, divorces or business sales. In fact, only one-third of family firms survive the transition to the second generation, and fewer than 10 percent survive to the third generation, according to the Owner Managed Business Institute, a Santa Barbara consulting firm.

One company at which a disagreement did not end so easily is Guess Inc. Founded in 1981 by the Algerian-born Marciano brothers Maurice, Paul, Armand and Georges Guess grew into a fashion powerhouse with its skintight jeans and steamy advertisements.

But in 1993, Georges resigned from Guess, after feuding with his brothers over the company’s direction. Georges reportedly wanted to start selling Guess products in mass-market retailers such as Wal-Mart and Sears, while his brothers wanted to limit the brand to upscale department stores. Georges sold his 38 percent stake in Guess then privately held to his brothers. Less than five months later, Georges sued Guess and his brothers for using the Marciano Collection label on Guess clothing a label Georges claimed he owned.

Georges reportedly no longer speaks with his brothers.

Kent Graham, an attorney with O’Melveny & Myers LLP who specializes in family-owned businesses, said the problems faced by businesses such as Guess are not all that different from those facing other companies. But, he said, the problems are exacerbated by family relationships.

“If you think about the dynamics of any family, there aren’t too many families out there that don’t have various levels of dysfunction,” Graham said. “When those dysfunctional family issues creep into the business, they’re magnified. Often the business becomes a surrogate for the disharmony going on in the family.”

One of Graham’s recent cases involved a couple who owned a business with their two children. There was such bad blood among the siblings that the business ended up being split into two, with each sibling taking control of one.

“They went their separate ways in terms of business, but it probably means they’re going to have a happy Thanksgiving together,” Graham said.

One of the most common problems facing family-owned businesses and the one that can often lead to personal relationships ending or a business being sold is succession.

“The greatest threats to the continuity of the family business are not estate taxes, laws governing corporations or the mechanics of stock transfers,” corporate consultant James W. Lea writes in his book “Keeping It in the Family: Successful Succession of the Family Business.” “The greatest threats are the nature of family relationships among siblings, between spouses and between generations and the personality of the founder or senior owner of the company.”

That seemed to be the case at Dart Group Corp., the parent company of Crown Books. In 1993, Herbert H. Haft ousted his son Robert, who conceived the discount Crown concept while a student at Harvard Business School and built it into the nation’s third-largest book retailer. The senior Haft later ousted his son from the board of the Crown Books Corp. subsidiary as well.

“It transcended business issues,” a Dart board member told the Washington Post at the time. “I close my eyes and I see two bucks standing at the top of a hill with the old one not ready to get out of the way.”

The result? Richfood Holdings Inc. bought the troubled Dart earlier this year, and Crown Books Corp. filed for Chapter 11 bankruptcy protection in July. In August, Crown began closing dozens of its stores, including 11 in L.A. County.

But not every family-run company is destined for destruction. Wareforce One Inc., an El Segundo-based seller of computer hardware and software, was one of L.A.’s fastest growing private companies before the marriage of owners Orie Rechtman and Anita Gabriel began to fall apart. Between 1996 and 1997, while the couple was having problems unrelated to the business, revenues were stagnant.

“Normally we would’ve had 50 percent growth,” Rechtman said. “When you stop functioning as two contributing partners, the growth is stalled.”

Last February, the divorce was finalized and Rechtman bought Gabriel’s share in the company, also taking over her title as chief executive. The company began to grow again, and Rechtman expects $140 million in revenues this year up from $89 million in 1996. In July, the company went public.

“It does affect the company when the two owners fight,” Rechtman said. “It’s like when two parents fight. It affects the children.”