 The Stiers had fled to America in the late eighteenth century as French Republican armies occupied their hometown of Antwerp.Calvert's father, the wealthy planter George Calvert (1768–1838), was the son of the Loyalist politician Benedict Swingate Calvert (c.1730–1788) – a natural son of the penultimate Proprietary Governor of Maryland, Charles Calvert, 5th Baron Baltimore – and Benedict's wife Elizabeth Calvert (1731–1788).Calvert completed his preparatory studies at Bladensburg Academy of Maryland.