Born in Canaan, CT to parents Revolutionary War Veteran, Jupiter and Fanny Mars. His fatherwas from Columbia County, New York, and his mother was from Loudin County, Virginia. Jupiter was enslaved by Canaan's Congregational minister, Amos Thompson who married Jane Evans (Fannie's enslaver). They had two children, James and Joseph. Evans wanted to relocate back to Virginia, so Thompson went with her to prepare. They left the Mars family in Canaan where they farmed in relative peace.