Todd was born about 1739 probably in Hunterdon County New Jersey to Irish Immigrants Robert Todd and his second wife Elizabeth. His ancestors were alleged to be Scottish rebels and Jacobites, Cavaliers in the Scottish Civil War who had raised the standard of rebellion too often and been exiled to Ireland from their native Angus, Scotland though documentary evidence of this has not been found. His parents were reported by a grandson to have emigrated from Ireland to America in 1737. Robert Todd was in Bethlehem Township, Hunterdon County New Jersey by 1743 until 1755 before coming to Chester County later in 1755 and then by 1760 to the portion of neighboring Philadelphia County that later became Montgomery County.