Complex sentence: Later, Moreau learns that his father was not the Count de Gavrillac, but rather the old Marquis de Maynes, Gavrillac's friend; the man he almost killed is his half-brother.
Split into simpler sentences: Later, Moreau learns that his father was not the Count de Gavrillac, but rather the old Marquis de Maynes. The man he almost killed is his half-brother.