Jackson and Hill were brother-in-laws. Here's how:
On November 2, 1848, Hill married Isabella Morrison, daughter of Robert Hall Morrison, the first president of Davidson College, a Presbyterian institution of higher education in Mecklenburg County, North Carolina. Mrs. Hill was a granddaughter of General Joseph Graham, who had seen extensive service in the Revolutionary War. An intelligent woman with requisite Presbyterian piety, Isabella had met "Harvey" while he was visiting one of his married sisters, who lived near Cottage Home, the residence of the Morrisons in Lincoln County, North Carolina.
In February, 1849, D. H. Hill resigned from the army and traveled with his young bride to Lexington, Va., where he accepted a position as a Professor of Mathematics at Washington College, now Washington and Lee University. It was here that he renewed his acquaintance with Thomas J. Jackson (1824-1863), later "Stonewall" Jackson, whom he had met during the Mexican War. Hill played no small part in Jackson's obtaining a teaching position at the Virginia Military Institute, also in Lexington, in 1851. Indeed, he recommended Jackson for the job. In 1857, Jackson became Hill's brother-in-law when he married Mary Anna Morrison, Isabella Hill's younger sister.