Siben died Tuesday. He was the firm's senior office administrator for many decades and still went to work once a week until he died, said his son Andrew, a managing partner of Siben and Siben.
The firm, founded in 1934 by elder brother Sidney, was known for taking on some of Long Island's most notorious cases. It represented victims of a pair of Long Island Rail Road accidents in the 1950s and an oil dealer who admitted spying for the Soviet Union in 1965.
Sidney died in January 2004, after brothers Walter and David had died.
"There was a bond of love there between the four brothers that was almost unimaginable," Andrew Siben said. "If one called in sick with a cold, the other three would call up with, 'How are you?' "
Born on Sept. 25, 1922 - he shared a birthday with David, born 10 years earlier - Aaron Siben was the youngest of the brothers. David ran a newsstand in Port Jefferson and helped put Sidney and Walter through law school. Sidney opened a law practice in Central Islip and was later joined by Walter.
Aaron Siben attended the University of Alabama on a football scholarship. Stocky and 5-foot-8-inches, Siben met Thelma Rosenthal, a health nut who told him, "When you lose 10 or 15 pounds, I'll be happy to see you." He did, and they were married in 1950.
After leaving college to join the Army, he saw heavy fighting in Italy and was listed as missing in action for several days, said a cousin, Claire Siegel of Patchogue.
"He crawled on his hands and knees for two days" until he reached Allied troops, said Andrew Siben, of Manhattan.
Another time in Italy, he was in the hospital with hepatitis when "the entire group of soldiers that he was fighting with was wiped out with bombs," his son said.
"He was wondering, 'Was there a reason for that?' "
Following his discharge, Siben joined his brothers' law firm as an office administrator.
Siben, a licensed real estate broker, lived in Bay Shore for 40 years and the last 10 in Manhattan. He was president for a number of years of the Bay Shore Jewish Center and served on the board of the Sandcastle co-op in Westhampton Beach, Siegel said. He was a patron of the Central Park Conservancy and the Metropolitan Opera.
In addition to his wife and son, Siben is survived by two daughters, Andrea and Melanie, both of Manhattan; a son, Lawrence of Manhattan; and a grandson. Services will be held at 11:30 a.m. Sunday at Bay Shore Jewish Center.