Alexander Sedlis is the son of Dr. Elias and Anna (nee Pruzan) Sedlis. He was born on May 17, 1921 in Vilna, Lithuania. Dr. Elias Sedlis (b. September 24, 1888) was a physician. He had served as a medical doctor and captain in the Russian army during World War I and later became the director of the Jewish hospital. Anna had served as a nurse in the Russian army. Alexander followed in his father's footsteps and attended medical school, while his younger brother Gabriel (b. January 1, 1924) studied studio arts at the Academy of Fine Arts.
Lithuania maintained its independence during the first year of World War II. However, during the summer of 1940, the Soviet Union annexed Lithuania and proclaimed it a Soviet republic. One year later, on June 24, 1941, Germany occupied Vilna. They immediately began the systematic slaughter of Vilna's Jewish population, but Alexander's family remained untouched. In July 1941 the Vilna municipality transferred the administration of the Jewish hospital to the Jewish community. Alexander and his fellow medical students went to work there as orderlies. Alexander first worked in the pediatric department. Doctors continued to care for the sick as if there was no war, and hospital personal gathered together in the hospital to share local news. During the many round-ups of Vilna's Jews at the killing site of Ponary, the families of health care workers hid in the hospital which served as a safe haven since the Germans stayed away for fear of contagious disease.
The Germans established a ghetto in Vilna in September 1941, but the Jewish hospital remained within the ghetto boundaries. The Sedlis family lived inside the hospital, and Elias remained as the chief physician. While in the ghetto, Alexander married a fellow physician, Emila Zeldowicz. She was the daughter of David and Henrietta Zeldowicz and was born in Vilna on April 20, 1922. Before the liquidation of the ghetto in September 1943, several hundred skilled workers and their families were transferred to labor camps outside the ghetto where they were shielded from immediate deportation. Alexander and Emilia went to the HKP (Heereskraftfahrpark/Ost/562) labor camp. There, the men worked in the German vehicle repair shops and the women in the kitchen or sewing shops. Major Karl Plagge, who ran the camp, was recognized by Yad Vashem in 2005 as Righteous Among the Nations. From there Alexander and Emilia went to Lida and Griciunai, Lithuania and Niemenczyn, Poland. Alexander's father, Dr. Elias Sedlis also survived as did his brother who had joined the partisans. Alexander's mother, Anna Pruzan Sedlis, perished in the Holocaust.