For three days and three nights, Joseph Davis — then Joseph Davidovich — rode in the crammed cattle car with his parents and six of his eight siblings. “We didn’t know where we were going,” he said. Finally the train pulled up to the Auschwitz platform. As the Jews were pushed from the cars, Dr. Josef Mengele, who was carrying a stick, hurriedly separated them. Joseph was directed to one side, torn from his family. His mother came running after him, carrying cookies she had somehow acquired, but a German soldier brusquely pushed her away. “That was the last time I saw her,” Joseph said.