Gaston was the younger brother of Odilon Redon (1840-1916). He studied architecture and was awarded the Prix de Rome in 1883. He later became professor at the Ecole des Beaux-Arts and worked for the Tuileries, Gobelins, Louvre, Fontainebleau and Compiègne. Gaston often turned to his older brother Odilon for advice. On 15 May 1872 he wrote him 'toi plus qu'aucun autre, peux me renseigner, me conseiller, me dispenser de certains travaux superflus. Pardon, pour tout ce que je réclame de toi, tu comprendra ce qui m'a poussé à te demander conseil'. When the Redon family decided to sell their house at Peyrelebade in 1897 Odilon stayed to see his brother.
Gaston's work was exhibited twice in 1931 and 1957. In 1877, Odilon Redon drew a portrait of Gaston, now in the Louvre (A. Wildenstein, Odilon Redon, Paris, 1992, I, no. 45).