Spiro was born in Berlin at the time of Nuremberg Laws. His father, Dr. Samuel Spiro, was removed from his job as a physician along with all other Jewish doctors, and settled in Jerusalem, Palestine in 1938. About half a year later, in March 1939, he was joined by his photographer wife, Grete Lina Spiro, and their two children, Gideon and his younger brother John Gabriel. The family lived in the Jerusalem neighbourhood of Kiryat Shmuel, which is between Katamon and Rehavia. Gideon’s father was employed as the chief doctor of Youth Aliyah, and after the Holocaust he treated the children of refugees from Germany and the children in Displaced Persons’ camps in Cyprus, as well as the Children of Tehran (a group of Jewish refugee children who escaped from Poland to Palestine via Tehran). Gideon was a graduate of the Hashomer Hatzair youth movement and the network of informal relations between teachers and students that he observed at a summer work camp on a kibbutz made a profound impression on him. He asked his father for permission to spend his secondary school years on the kibbutz, and in 1951 he moved to Kibbutz Merhavia, where he was influenced as a youth by the principles of equality and social justice. Three years later he was conscripted into the IDF and volunteered to join the paratrooper corps, and took part in the reprisal actions of the 1950s and in the jump at the Mitla Pass in the Sinai War of 1956.