Maurice Greenberg, the founder of the insurance giant A.I.G., is making a comback, quietly building up a family of insurance companies that can compete with his old outfit at his venture C.V. Starr & Company. By limiting pay at A.I.G., the United States Treasury is lending Greenberg a hand, assisting with the exodus of talent from the old firm to the new one. "Basically, he’s just starting 'A.I.G. Two' and raiding people out of 'A.I.G. One,'" said an insurance executive. Greenberg was pushed out of A.I.G. after an accounting scandal in 2005. He is 84.