A renowned “teacher of teachers,” Greenberg’s scholarly father, Sam Genauer, who was born in Czernovitz, Austro-Hungary in 1906, was brought to the United States at the age of two. He obtained a B.A. at Yeshiva University and in 1933 was ordained at its Rabbi Isaac Elchanan Rabbinical College. His homemaker wife, Sylvia (née Gensar), whom he married in 1933, was born in the Lower East Side of New York in 1913 and attended Seward Park High School and the University of Washington. Immediately after his ordination the couple moved to Seattle, where Genauer managed his family’s clothing business. It was there that their three daughters were born: Judy (Brickman) in 1934, Blu on January 21, 1936 and Rena (Schlaff) in 1938. The family returned to New York when Blu was in the fifth grade.