Results are mixed. There can be a big upside. Family firms generate distinctive and powerful cultures through the infusion of family capital ¬ the ethos, values and pragmatism of an adaptive and loving family ¬ which has been proven to enable them to outperform and outlast non-family businesses.

But there is a downside. Many family businesses fall by the wayside because they are unable to get the mix of reason and feeling right.

In our book, Family Wars, Grant Gordon and I analyse 24 high-profile family business conflicts from around the world. Many of them fail because of individuals: demonic, overbearing father-bosses, or vengeful children fighting for ownership and power. Many suffer through poisonous relationships. Brothers go at each other like wildcats in a sack.

Some run into trouble through family insularity. They stack the business with family members and turn a blind eye to the outside world.

Others are driven by factionalism. Inequitable divisions of ownership, power or wealth create warring tribes of haves with have nots.

Yet many of our cases survive the conflicts and go on to become businesses that still thrive today, such as Ford, Reliance, IBM and U-Haul.

But all of them could have saved themselves a lot of trouble had they heeded a few simple lessons. Here are ten.

• Look at your family. Is it in good shape to run a business? If you can foresee insoluble jealousies and power struggles being amplified by the rigours of shared ownership or management, then let family members go. Bring in the professionals, or sell up and be happy.

• Watch out for the warning signs of conflict before it breaks out. In our book we list 20 such signs, including complaints about unfairness, communication gaps, delays in making critical decisions, a strategy of too much consensus, injurious gossip, and the emergence of factions.

• Be aware of the most common causes of family conflict, and head them off at the pass. Poor parent-child and sibling relationships can be the biggest issues of all. Don’t force incompatible people into unnatural co-operation.

• If the family is in total control of the business and pursuing its own path, however successfully, don’t let it become isolated from the outside world. Solicit genuinely independent voices to give you a reality check and diagnosis of points of weakness, deficiency or risk.

• Watch out for dangerous narrative. These are the stories that family members spin, caricaturing and exaggerating rights and wrongs, family good guys and bad guys.

• Don’t set rules that turn into poisoned games of winners and losers, such as tournaments for succession among family members, or battles for control among family members forced unwillingly into harness with each other.

• Create disciplines. Family firms are often light on structure, governance and rules. In a growing business you will need and benefit from the best kinds of formality sooner than you think. Don’t just trust instinct.

• Forgive and forget. No matter how bad things get, treat the present situation as a blank slate with no history. It’s hard to do but it’s necessary. Put your heads together and figure out what a smart stranger parachuted into your world would see as obviously the best thing to do right now.

• Always remember to look up towards the ultimate common interest that unites your family, rather than down at the recent, local and close issues that divide you. Rise above the petty and selfish; find, honour and protect what is going to be the lasting legacy of your business.

• Remember, your family culture is potentially a source of unique competitive advantage. Celebrate and embody your values.

Nigel Nicholson is a professor of organisational behaviour at London Business School and co-author with Grant Gordon of Family Wars: Classic Conflicts in Family Business and How to Deal with Them