Erasmus Burt was born around 1820 in Edgefield County, South Carolina. He was one of ten children of Francis Burt, a member of South Carolina House of Representatives from 1798 to 1800, and Catherine Miles. His brothers included Armistead Burt (November 16, 1802 – October 30, 1883), who was elected to Congress in 1843 for South Carolina and served until 1853 and who was married to the niece of John C. Calhoun, and Francis Burt (January 13, 1807 - October 18, 1854), who served in Washington, D.C. as the Third Auditor of the Treasury, and in 1854 was appointed the first Territorial Governor of Nebraska.