In September last year, one of the biggest stories on the insurance world was how the driving force behind AIG, the US insurance giant, Maurice "Hank" Greenberg, had seen his two sons quit the company, raising questions about who would lead it in the future.

The most recent heir apparent, Evan Greenberg, defected, leaving father without a replacement.

Over a year on, he still has not been replaced, but on Monday night ACE Ltd. announced they had lured Evan Greenberg into the fold as vice-chairman and head of the company's reinsurance, ACE Tempest Re.

And while it is a big coup for ACE Ltd. to get such a big fish into their pond, it is the story behind the Greenberg family that has headlines over and over again.

Greenberg senior, the chief executive of American International Group, has seen three decades at the helm of the mighty insurance giant, something that has made him a revered and feared figure in the financial services industry. But Greenberg the elder, who has an estimated net worth of $4 billion, saw his plans for handing over his realm to his children go awry as his children left the fold.

Early in 2000, it seemed that the 76-year-old patriarch of the world's largest public insurer had capped the many triumphs of his career by appointing 46-year-old son Evan as his successor, starting a corporate dynasty with the blessing of AIG's directors and investors.

But things suddenly changed in September when Evan Greenberg, who was set to become only the third chairman in AIG's 81-year history, resigned abruptly as its president and chief operating officer.

His resignation came nine months after Greenberg senior, the most prominent figure in the US insurance industry, said his son would "absolutely" succeed him. Shares of AIG, the world's largest insurer, rose almost two percent to $90.13 after the announcement.

No reasons were given for the departure but the son left behind tens of millions of dollars of potential share option profits, and a father without an obvious successor. Greenberg the elder has not named a new successor since Evan left AIG, and has not yet announced any plans to retire.

Evan's sudden departure, aged 45 at the time, was all the more remarkable because it echoed the resignation five years before of his older brother.

Jeffrey Greenberg, a talented lawyer, had been similarly set up to succeed his father before jumping ship without warning to run Marsh & McLennan, the rival insurer.

The Financial Times quoted head-hunters with links to AIG as saying both sons chafed at the demands placed on them by their exacting father, who was unwilling to cede enough responsibility.

Hank Greenberg is said to remain in good health. Company legend has it that the AIG jet is equipped with an exercise bicycle, and Mr. Greenberg has cultivated his image as a fitness fanatic who eats grilled fish each day, and enjoys out-skiing men half his age at Stowe, the Vermont resort owned by AIG.

The Financial Times said that Evan Greenberg would prepare for meetings with his father - a famously tough boss - by insisting colleagues give him detailed briefings.

The son's style could be as robust as his father, associates say, but the differences were notable. Whereas Hank was part of the World War II Normandy invasion force, Evan ducked out of university to travel around America for three years and work as a bartender before joining the corporate fold.