Reinhard Heydrich was of German and Jewish ancestry.
Reinhard Tristan Eugen Heydrich was born on March 7, 1904, in Halle an der Saale, 20 miles northwest of Leipzig, in the German state of Saxony. Heydrich's father, Bruno Richard Heydrich, was a musician, opera singer, and composer. He was the director of the music conservatory in Halle, which he had founded in 1901.
Bruno's father was a carpenter but had died in 1916. His mother married a mechanic named Gustav Süss. Although he was not Jewish, Süss was a common German-Jewish name at the time. The clear implication is that Heydrich senior was Jewish, and throughout his life, Reinhard Heydrich sought to suppress details of his Jewish ancestry. From his mother's gravestone, he is said to have erased the suggestive forename, Sarah.
Heydrich's mother, Sarah Elisabeth Krantz, a Roman Catholic, was the daughter of his father's teacher, who was the director of the Royal Conservatory of Music in Dresden. According to André Brissaud, the author of the Nazi Secret Service (1972), Reinhard Heydrich's grandmother was Jewish.
As a boy, he lived in an elegant home with his family enjoying elevated social status. But young Heydrich also suffered as the target of schoolyard bullies, teased about his very high pitched voice and his devout Catholicism in the mostly Protestant town. He was also beaten up by bigger boys and tormented with anti-Jewish slurs amid rumors of Jewish ancestry in his family.
At home, Heydrich's mother believed in the value of harsh discipline and frequent lashings. As a result, Heydrich was a withdrawn, sullen boy, unhappy, but also intensely self-driven to excel at everything.
During World War I and its aftermath, Bruno Heydrich could barely keep the conservatory open due to the economies imposed by the war. As his family struggled economically, Heydrich, still in his teens, was attracted to racist (völkisch) nationalism. He watched demonstrations, strikes, and street battles in Halle during the last year of the war and the revolutionary chaos that followed. At 15, he joined the paramilitary Maracker Freikorps, a band that fought against revolutionary groups in Germany. He later enlisted in a home defense force and joined the Deutscher Schutz und Truzbund, a nationalist and anti-Semitic organization.