At ACE he was eventually succeeded as CEO by Evan Greenberg, the son of the former AIG chief executive. Mr. Duperreault had been a mentor to the younger Evan Greenberg at AIG and hired him for a senior job at ACE. At Marsh Mr. Duperreault took over a post held at one time by Evan Greenberg's brother, Jeffrey. The new CEO of AIG will have to re-establish leadership for a company that received a $185 billion government bailout during the last financial crisis and is now under pressure from activist investors for lackluster financial results. In March, AIG announced Mr. Hancock would resign after less than three years at the helm. Many board members were unhappy about recent setbacks in the company's plan for boosting profitability, said people familiar with the matter, while several also feared a potential fight with activist investor Carl Icahn. Mr. Hancock agreed to stay until a successor was found. Mr.