Mr. Avellino did not respond to calls or visits to his homes in Nantucket, Mass.; Palm Beach, Fla.; and New York, or to messages left with his son Joseph Avellino in Chester, N.J. Gary Woodfield, the former federal prosecutor who represents Mr. Avellino, also declined to comment. Francis B. Brogan, a longtime lawyer for Mr. Avellino and a partner at Greenberg Traurig in Fort Lauderdale, Fla., asked that questions be e-mailed to him, then did not respond.

Mark Raymond, a lawyer for Mr. Bienes, said that his client had no knowledge of Mr. Madoff’s fraud and had lost tens of millions of dollars, most of his savings, in the fraud. Mr. Bienes worked mainly as a fund-raiser, while Mr. Avellino actively managed Avellino & Bienes, according to court documents and people who knew the men.

Mr. Avellino has been connected to Mr. Madoff for his entire career. After graduating from the City University of New York in 1958, Mr. Avellino began working as an accountant at a firm run by Saul Alpern, Mr. Madoff’s father-in-law.

Mr. Madoff also briefly ran his securities business from the firm’s offices. As early as 1962, according to the S.E.C.’s complaint against him, Mr. Avellino began raising money for Mr. Madoff, who was running a small brokerage company. Mr. Bienes joined in 1965.

In 1977, Mr. Avellino and Mr. Bienes formed an accounting firm in Midtown Manhattan. Mr. Avellino owned half the company; the remainder was owned by Mr. Bienes and his wife, Dianne. In 1980, the Bieneses moved to Fort Lauderdale, while Mr. Avellino remained in New York.

The two men gradually shifted their focus from accounting to raising money for Mr. Madoff. Their business expanded until 1992, when the S.E.C. received marketing materials showing that Avellino & Bienes had promised investors annual returns of up to 20 percent. Commission officials said at the time that they believed they had stumbled upon a Ponzi scheme.

Image Michael Bienes with his wife, Dianne, in 2005. Mr. Bienes and Frank Avellino ran Avellino & Bienes, a now-defunct firm that used to funnel investors to Bernard L. Madoff. Credit... Walter Michot/Miami Herald

But when the investigators went to Mr. Avellino, they found, to their surprise, an apparently legitimate explanation. The money, $441 million from 3,200 clients, was being managed by Mr. Madoff, whose brokerage firm by then was one of the biggest stock traders on Wall Street. In a deposition, Mr. Avellino explained that he had promised returns of 13.5 to 20 percent a year. If Mr. Madoff fell short of producing those returns with his stock trades, Avellino & Bienes would make up the difference, Mr. Avellino said.