Johann Georg was the son of Franz Mozart, a master mason. However, Johann Georg pursued a different career, becoming a master bookbinder. He evidently advanced his career when he married Anna Maria Banegger, widow of his former master, and thus obtained his old master's guild license. His first wife bore him no children and died in 1718. His second wife was Anna Maria Sulzer (1696–1766), with whom he had 8 children over the years 1719–1735; 3 boys and 2 girls survived to adulthood. Leopold, born 14 November 1719, was the oldest.
The family were Catholics and after 1722 lived in a house owned by the Jesuits. They sent their two oldest sons to Jesuit schools.
Neither Johann Georg nor his wife Anna Maria had any direct influence on the life of their celebrated grandson. Johann Georg died 20 years before Wolfgang Amadeus Mozart was born; and Leopold became estranged from his mother following his move in young adulthood to Salzburg (1737); hence there was no contact between grandmother and grandson during the period their lives overlapped.
Another son of Johann Georg, Franz Aloys Mozart (1727–1791), remained in Augsburg and followed his father's career as a bookbinder (he also occasionally published religious tracts). He was the father of Maria Anna Thekla Mozart, Wolfgang's first cousin and friend.