Jean Coulliard was a member of the human settlement of Olympus on Mars, and brother to Legrand Antoine Couillard. In Martian Dreams, the Avatar first met Jean's brother, Legrand, who had been ordered by Jack Segal to guard the smashed-up Dream Machine. Legrand was highly upset and concerned over the fate of Jean, who had ventured into the Olympus mines for more ore, but had not yet returned. Legrande agreed to let the Avatar's group in to see the Dream Machine if they first searched for his brother in the mines.