Julius Rietz and Eduard Rietz were brothers. Eduard Rietz was the older brother, and Julius Rietz was his younger brother. They were sons of the violist Johann Friedrich Rietz.
Julius Rietz took his first music lessons from his older brother Eduard Rietz. After Eduard Rietz's untimely death in 1832, Felix Mendelssohn, who had been a friend of Eduard Rietz, supported Julius Rietz. Eduard Rietz had been Mendelssohn’s first violin teacher, and their friendship was partly inherited by Julius Rietz.
