Sidney J. Weinberg Jr., a senior director at Goldman Sachs & Co. and a member of the family central to the firm's modern history as an investment bank, died Monday of prostate cancer at age 87 in his home in Marion, Mass.

Born in Scarsdale, N.Y., he joined the New York firm in 1965 as a general partner and ran Goldman's investment banking division from 1978 to 1988. He became a limited partner in 1988 and a senior director in 1999, when the firm went public.

Weinberg’s father, Sidney J. Weinberg, was Goldman’s chief executive from 1939 to 1969, while his son, Peter, worked for Goldman for 17 years and is a founding partner at investment bank Perella Weinberg. His brother, John Weinberg, was partner at Goldman from 1976 to 1990 and died in 2006. His nephew, John S. Weinberg, is a current vice-chairman at Goldman and co-head of investment banking.

Weinberg Jr. served in the U.S. Army, assigned to the Philippines during World War II. He earned his bachelor’s degree at Princeton University in 1947. Two years later, he received his master’s degree in business administration from Harvard University. Weinberg Jr. rose to vice president of the textile division of the Owens Corning Co. before joining Goldman Sachs.