John Alfred Brashear was born on November 24, 1840 Brownsville, Fayette County, Pennsylvania. He belonged to a family of French Huguenots named Brasseuir who emigrated to America and settled in Calvert County, Maryland, in 1658.
In 1775 a descendant of this family, Otho Brashear (the original Brasseuir had undergone several changes in spelling), emigrated from Maryland to the present site of Brownsville, Pennsylvania. Here his grandson, Basil Brown Brashear, a saddler by trade, married a schoolteacher, the daughter of one Nathaniel Smith, who had emigrated to Brownsville probably from Massachusetts. John Alfred Brashear was the first of their seven children.