The Syphax family apparently descended from a "Mulatto man" named Syphax who was purchased from Henry Ennalls, Jr., of Dorchester County, Maryland, by Armistead Churchill of Middlesex County, Virginia. He ran away from Churchill with a white servant named John Johnson on 9 June 1752. Churchill placed an ad in the 12 June 1752 issue of the Virginia Gazette (Rind), describing Syphax as

a Blacksmith...a likely brisk young Fellow, the fore Part of his Head shaved, and the back Part long Wool.

William, Betty and Caty Syphax were apparently servants bound to Hannah Churchill on 15 March 1776 when she left them to her son Benjamin Churchill "until they are free" by her Middlesex County will which was proved on 25 November 1776 [WB F:83].