Robert Hunter Hancock was born on May 1, 1813, in Circleville, Ohio, the fourth of the fourteen children of Mary Martha (Harbert) and Dr. Johnson Calhoun Hunter. The family moved to Texas in March 1822, after a sojourn in Missouri, and in April 1829 moved to Fort Bend County, where the following month the sixteen-year-old Robert Hunter received a grant of one-third league. He joined Capt. James Franklin Perry's company of volunteers and participated in the Grass Fight and the siege of Bexar, but when Lt. Col. William B. Travis issued his appeal for aid in defense of the Alamo, Hunter and his brother John Calhoun Hunter joined Capt. John Bird's company. Its march to San Antonio was intercepted by the news that the Alamo had fallen; Bird's men joined Sam Houston's army as it retreated across Peach Creek. Hunter remained with the army through the San Jacinto campaign, but, perhaps because he was armed only with a Harpers Ferry jaeger rifle, the lock of which "was tied on with a buck skin string" and the "stock & barel was tide to geather with buckskin," he was detached to help guard the baggage train at Harrisburg during the battle. Afterward he was detailed to guard Gen. Antonio López de Santa Anna.
After the Texas Revolution Hunter returned to Fort Bend County, where he engaged in farming and stock raising. By 1840 he reported owning a saddle horse, a silver watch, and twenty-five cattle. The next year he married Samirah M. Beard. The couple had seven children. In January 1845 he moved to Guadalupe County, established a farm and, with his father-in-law, a saw and grist mill on San Geronimo Creek some two miles south of Seguin. In 1850 Hunter estimated the worth of his real estate at $4,000. In 1857 he sold the mill for thirty dollars and moved to Victoria, where in 1860 he composed a colorful and informative reminiscence, based on his diary of his early days in Texas and his role in the Texas Revolution. The manuscript is preserved in the Texas State Archives. In 1936 Beulah Gayle Green edited and published the memoir as the Narrative of Robert Hancock Hunter, 1813–1902. John H. Jenkins III considered this one of the basic Texas books, and Carlos Castañeda referred to it as "the best account of the San Jacinto campaign left by a veteran." In 1880 Hunter moved to the vicinity of Flatonia in Fayette County. There his wife died in April 1888. Hunter was a Methodist, a member of the Texas Veterans Association, and for most of his life a Democrat. With the rise of populism, however, he shifted his allegiance to the People's party. His brother Thaddeus is said to have been the first White male born in Stephen F. Austin's colony. Hunter died near Flatonia in 1902.