Joseph Sr. was the son of Edward Hart and Nancy Stout. He married Mary Kittle on 11 Apr 1819 in Beverly, W.V. They had three children:

Emily
Nancy Ann
Milton

When Mary died, Joseph remarried to Susan Pickens on 8 Oct 1826 in Randolph Co., West Virginia. They had ten children together:

Elizabeth
Martha
Mary
David Blackman
Rebecca
George Daniel
Maria
Squire Bosworth
Joseph Jr.
Alexander Pickens

"Joseph Hart grew up in the town of Beverly and received his education in the local schools. He taught school for a time. Then he became a Baptist preacher. The Randolph County Marriage Records show that he performed 47 marriages from May 22, 1822 to October 10, 1827. It is also said that he studied medicine. In 1850 and 1860 Randolph Co. Census, he gave his occupation as farmer. Then his interest turned to politics. According to Swem and Williams Register of the General Assembly of Virginia, page 385, he served in the House 1827/28, 1829/30, 1830/31, 1831/32. His name first appeared in the Randolph Co. Court Records as a Gentleman Justice in 1830, having been appointed by the Governor of Virginia, and her served in this office as late as 1860. In those days, justices made up the county court which ran the business of the county including the work of the circuit court. In 1833 and 1834 Joseph Hart served as deputy sheriff for his brother-in-law, George Stalnaker, sheriff. In 1835 he acted as deputy sheriff for Isaac Booth. In 1837 his name first appeared in the court records as a lawyer. It is believed he worked with David Goff, another lawyer in Beverly." Pg. 141, The Harts of Randolph, 1976.
Sources
The Harts of Randolph or Mostly Descendants of Edward and Daniel Hart, sons of John Hart, The Signer, Complied and Edited by Katherine Hart Frame McClain Printing Company, Parsons, West Virginia, 1976
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Joseph Hart taught school for awhile and, as a Baptist minister, performed 47 marriages. He served four terms in the General Assembly of Virginia and as a "Gentleman Justice" from 1830. During the Civil War, he was appointed prosecuting attorney by the Union-loyal Reorganized Government of Virginia. As such, he was a hunted man by Lee's army. He and his family left their home in West Virginia, scattering throughout the country—a story that is eerily similar to his grandfather, John Hart.