Rawlins Lowndes was born in January 1721, in St. Kitts, West Indies. He was the grandson of Charles Lowndes who was probably a younger brother of Richard Lowndes of Cheshire, England, an ancestor of Lloyd Lowndes. He was the son of Charles Lowndes who emigrated, first, to St. Kitts, where he married Ruth, the daughter of Henry Rawlins, an influential planter. In 1730, on account of financial difficulties, the family went to Charleston, South Carolina, where the father died when Rawlins was about fourteen years old. The widow returned to St. Kitts, leaving her son in the care of Robert Hall, provost-marshal of the colony.