On 26 September 1863 in Altona, Bronsart von Schellendorf married Harriet Donner (born 14 November 1841 in Altona; died 21 September 1917 at Gut Marienhof, Amt Güstrow), the daughter of the Hamburg business magnate and banker Bernhard Donner, adviser to the Danish government and landowner at Schloss Bredeneek, and of Helene Schröder (from a baronial family).

He was the younger brother of Paul Bronsart von Schellendorff, and became Minister of War 10 years after him.

Bronsart von Schellendorf left cadet school in 1851 and joined the 1st Infantry Regiment and was promoted to Lieutenant in 1852.

After studying at the Allgemeine Kriegsschule (General War College; later the Prussian Military Academy) from 1855 to 1858 he was made adjutant of the I Corps in 1859, after having been assigned to the 8.

In this capacity, he defended the army against the criticisms of the Social Democrats, and announced a reform of the military criminal justice procedure as demanded by the Reichstag.