Battle Over $ 20 Billion in Insurer 's Stock Escalates A legal battle over nearly $ 20 billion of stock in American International Group , the insurer , escalated , as lawyers for Maurice R. Greenberg , A.I.G . 's former chief executive , argued in a lawsuit that the shares belong to Starr International , which is headed by Mr. Greenberg , and not to A.I.G . -LRB- C3 . -RRB-