Brown was born on March 1, 1812, in Bridgewater, New Hampshire,[1] the son of Benjamin Batcheldor and Mary Spaulding.

[2] Simeon married Adeline Brown in 1834, with whom he had his only child, Samuel, on January 1, 1839, who would go on to serve in the 5th New Hampshire Infantry Regiment.

[1][3] On August 14, 1863, he was promoted to colonel, and on December 10 of the same year, he was given command of the newly formed 11th Michigan Cavalry Regiment.

He would lead the regiment at the Battle of Cynthiana during Morgan's Raid into Kentucky.

He was then promoted to brevet brigadier general on January 1, 1865 and took part in Stoneman's 1865 raid as commander of three Cavalry Regiments.