On his mother's side, Rabbi Orenstein's family were expelled from Spain in 1492, then migrated to Turkey. He has both Sephardi and Ashkenazi roots, and his parents were true sabras, born in Israel before and shortly after it became independent in 1948. His father fought in the Six Day War of 1967 and the Yom Kippur War in 1973. The family moved to Canada shortly after the Yom Kippur War, and settled in Winnipeg. Rabbi Orenstein studied medical science at McGill University, while at the same time pursuing Jewish theological studies. He finally decided to become a rabbi, was ordained, and became assistant rabbi at the Shaar Hashomayim synagogue. He later became Rabbi at Shaarei Tefilah synagogue in West Vancouver, before coming to The Spanish and Portuguese Synagogue, where he is currently the Rabbi.
