Eduard Klein was the older son of Richard and Maria Klein. The Kleins were a family of hidden Jews living in Berlin. His infant brother, Paul, was diagnosed by their pediatrician, Martin Dambach, with Tay-Sachs disease, a condition more common in Jews than in others. Eduard was too young to know that he was Jewish. He was also well indoctrinated with the Nazi ideology regarding the diseased and the disabled, and was not at all troubled by the fact that his infant brother was euthanized by his parents.