[citation needed] The Critical Dictionary of English Literature and British and American Authors (1897) has the following entry about her: Rebecca's father was the jurist Jacob Rush.
[1][2] Her mother was Mary "Polly" Rench who married Jacob Rush on November 17, 1777 in Pennsylvania, while avoiding the British Army which had occupied Philadelphia.
[citation needed] Rebecca's uncle was Dr. Benjamin Rush, signatory to the 1776 Declaration of Independence.
[citation needed] Another uncle was Dr. James Rench of Cedar Creek Hundred, Sussex County, Delaware, a member of the Delaware Assembly and lieutenant colonel of the Sussex Co.
[citation needed] Rush's uncle by marriage, husband of Sarah Rench, was the colonial portrait painter James Claypoole, Jr.[citation needed] Rush's maternal grandfather, Captain Walter Rench, a ship master, was lost at sea some 14 years before her birth.