John Baer was born to Bernhard and Marta Baer on April 26, 1917 in Breslau, Germany (today Wrocław, Poland). His father was a sales representative for fur and textile manufacturers and his mother owned a millinery store. John had an older sister, Lilly. He received his elementary and secondary education in public schools in Breslau, and also attended a Hebrew school.

Betty Berz (née Sagal) was born on June 22, 1926 in Kyiv, USSR (today, Ukraine). The family—Betty, her mother Marie, her father Boris, and her younger sister Rachel—immigrated to Paris in 1929.

Maurice Blindt was born on February 20, 1924, to Samuel and Fajga Blindt, both of whom were originally from Poland. He had a sister, Lucia, born in 1919, and a
brother, Henri, born in 1926. On the eve of World War II, Lucia left Paris to live in Algiers. When Germany invaded France in May 1940, the Blindts fled Paris. In the process of fleeing, they encountered heavy gunfire and arial bombings, and Fajga had a nervous breakdown.

Lajos Cséri (name at birth Lajos Klein) was born on January 22, 1928 in Hajdúböszörmény, Hungary, in a secular Jewish family. Lajos had a brother, Gyula, and a sister, Anna. He attended a Protestant school in Sárrétudvari, where he spent most of his childhood.