Rosenzweig was born in 1929 in Ksiaz Wielki, a village 25 miles from Krakow in southern Poland. He was the oldest of five children and had two brothers, Yakov (b.1932) and Laibel (b.1934), and two sisters, Zisel Zysl (b. 1930) and Raizel (b. 1936). His mother, Chana, was a housewife and his father, Chaim, was a businessman.