Background: Josef Mengele (German: ['jo:zef 'meNG@l@]; 16 March 1911 - 7 February 1979) was a German Schutzstaffel (SS) officer and physician in Auschwitz concentration camp during World War II. Mengele was a member of the team of doctors responsible for the selection of victims to be killed in the gas chambers and for performing deadly human experiments on prisoners.
Context: Mengele was born the eldest of three children on 16 March 1911 to Karl and Walburga (Hupfauer) Mengele in Gunzburg, Bavaria, Germany. His younger brothers were Karl Jr and Alois. Mengele's father was founder of the Karl Mengele & Sons company, producers of farm machinery. Mengele did well in school and developed an interest in music, art, and skiing. He completed high school in April 1930 and went on to study medicine at Goethe University Frankfurt and philosophy at the University of Munich. Munich was the headquarters of the Nazi Party. In 1931 Mengele joined the Stahlhelm, Bund der Frontsoldaten, a paramilitary organization that was absorbed into the Nazi Sturmabteilung (Storm Detachment; SA) in 1934.  In 1935, Mengele earned a PhD in anthropology from the University of Munich. In January 1937, at the Institute for Hereditary Biology and Racial Hygiene in Frankfurt, he became the assistant to Dr. Otmar Freiherr von Verschuer, a scientist conducting genetics research, with a particular interest in twins. As an assistant to von Verschuer, Mengele focused on the genetic factors resulting in a cleft lip and palate or cleft chin. His thesis on the subject earned him a cum laude doctorate in medicine in 1938. Both of his degrees were later rescinded by the issuing universities. In a letter of recommendation, von Verschuer praised Mengele's reliability and his ability to verbally present complex material in a clear manner. The American author Robert Jay Lifton notes that Mengele's published work did not deviate much from the scientific mainstream of the time, and would probably have been viewed as valid scientific efforts even outside Nazi Germany.  On 28 July 1939, Mengele married Irene Schonbein, whom he had met while working as a medical resident in Leipzig. Their only son, Rolf, was born in 1944.
Question: Did he have any siblings?. Whats the answer?
the eldest of three children