Mark Madoff, the older of Bernard L. Madoff’s two sons, hanged himself in his Manhattan apartment in December 2010, the second anniversary of his father’s arrest for running a gigantic Ponzi scheme that shattered thousands of lives around the world. Mr. Browne said the body was discovered by Martin London, a prominent New York lawyer who is the stepfather of Mark Madoff’s wife, Stephanie. Mr. London apparently had gone to the apartment in response to the message to check on the child. Mr. Madoff had expressed both continuing bitterness toward his father and anxiety about a series of lawsuits that were filed against him, his brother Andrew and other family members. Mr. Madoff, 46, was among the directors and officers of a Madoff affiliate in London who were sued by the trustee seeking assets for victims of the scheme. Mark Madoff had been a licensed broker at his father’s firm since June 1987. A number of Mark’s oldest childhood friends from Roslyn, N.Y., invested with the Madoff firm and lost their savings in the fraud, said another person who was close to the family. This destroyed those relationships and caused Mr. Madoff great pain. And on the advice of his lawyer, Mark Madoff has had no contact with his parents since the day before his father’s arrest two years ago. At the University of Michigan, his social circle included students largely from other well-to-do East Coast families. He graduated in 1986 and moved to New York to join his father’s firm. Most of his friends rented crammed studios, but Mark lived in an apartment his father had bought for him in Sterling Plaza, a luxury high-rise on Manhattan’s East Side developed by Sterling Equities. Sterling is controlled by Fred Wilpon, the owner of the New York Mets, whose family was friendly with the Madoffs and whose businesses had invested hundreds of millions of dollars in the Ponzi scheme. Mark Madoff married his college girlfriend, Susan, and moved to Greenwich, Conn., where they raised two children. They divorced in the 1990s and Mark eventually moved back to Manhattan. He was remarried, to Stephanie Mikesell, and had two more children with her.