Antisthenes, a disciple of Socrates, observed: "When brothers agree, no fortress is so strong as their common life."

Bonds of brotherhood come in handy in business. Scads of studies indicate that family-owned companies (which account, by some estimates, for 50% to 70% of global GDP) have a competitive edge over the rest. But those bonds can unravel at a frightening pace too--and plenty of families don't see it coming.

Here's the all too typical arc: When brother-owners first face a common enemy--interest payments, ornery customers, feckless employees--they tend to work in tireless harmony. There is no time for dusty, unresolved conflicts. (If your livelihood is threatened, who cares if Dad spent more time with your brother than you?) It's when things start getting good that those old ghosts start jangling their chains.

Just ask Javier Ibanez, co-owner of Three Brothers Mexican Buffet, now with 18 locations throughout the U.S. (The names here have been changed, but the characters are real.) Born to a poor family in Guadalajara, Mexico, Javier dreamed of running a business with his two younger brothers, Joaquin and Jaime. "I worked six days a week for eight years [as a waiter in San Diego] so I could bring my brothers here from Mexico," says Javier. "Who else would you trust to build a business with?"

When the Ibanez brothers opened their first location in San Diego in the early 1980s, they were a well-oiled, unrelenting unit. A few years later, with four locations up and running, Javier made what would prove a deleterious decision: He decided to expand the operation. Javier went on the road to scout locations in major cities that had significant Hispanic populations. Joaquin, the second oldest brother, and Jaime, the youngest, would remain in San Diego.

Out popped the ghosts--specifically Jaime's. As a physically weak and emotionally insecure child, Jaime was teased by his six siblings (he had four sisters) with the exception of Javier, his protector. When, at age 16, Javier left the family for San Diego, Jaime, then only 6, felt abandoned, resentful and terribly scared. Jaime would confide to me later than he had repressed those feelings for decades.

When those memories came roaring back, the friction was fierce. If Joaquin disagreed with Jaime (about everything from adding a menu item to the likely outcome of a San Diego Chargers football game), Jaime would lash out, even cry. If Joaquin made a minimal request of his brother, Jaime would defiantly shout: "I’m your partner, not your slave," and stomp off.

Making matters worse was a rather Machiavellian operations manager who tried to use the brothers' conflict to his advantage. Every time Jaime started shouting at Joaquin, the manager rushed to Jaime's side--all the while stoking Jamie's frustration with Joaquin and extracting favors such as hiring his relatives, taking extended weekend breaks and giving himself a company car. When Javier got wind of all this, he fired the manager, sending Jaime further into a tailspin. At his pique's pitch a year ago, Jamie accused his brothers of plotting against him and resigned from the company.

Within weeks, the brothers had coaxed Jaime back into the fold. But they still had a big problem: How to restore the unity that served them so well as both a family and a business? My answer to them when they sought my help: Air it all out.

I walked the brothers through a number of role-playing exercises that involved having them raise a concern and resolve it. It took some effort, but eventually Jaime opened up about how he felt about Javier going on the road to expand the business. When Jaime spontaneously blurted, "Javier, you have been my salvation my entire life," it was Javier who broke down in tears.

Too touchy-feely for you? Today, the brothers end each work week with a "decompression meeting," where they hash out any raw feelings. The rule of thumb for these sessions is that no issue is too trivial, and no one leaves the meeting harboring a grudge. More often than not, as with other family owners I've worked with, those chats lead to a hearty chuckle--each one another brick in that fortress.