Benoît Gillain is the oldest son of Jijé. He started out making cover illustrations for Le Moustique magazine, and had an advertising agency in Paris. He is the creator of 'Bonux-Boy', a character that was used for advertisements of Bonux washing powder in the 1950s and 1960s. The character originated in 'Bouby', a comic strip that Gillain had created for Panorama Chrétien in 1958. Benoît, or Benoist, as he signed his work, initially drew several one-page and two continuing stories to promoted goodies that came with the Bonux powderboxes. These stories were printed in children's magazines like Spirou around 1960.
Inspired by the Spirou mini books, Bonux-Boy was eventually featured in a series of at least 18 mini comics in 1960 and 1961. Besides new (and longer) stories with 'Bonux-Boy' (for which Benoît was aided by his father), these booklets also contained work by Jijé, Peyo, Will, Roba, Jidéhem, Bara, Mouminoux, Follet, Herbert, Craenhals, Deliège, Azara and Giraud. In Italy, the character was renamed to 'Tidino' and used for the promotion of Tide washing powder. Benoît Gillain later headed Benoit Gillain Design et Commucation, where some of his clients were Lanvin, Givenchy and Fnac.
Between 1966 and 1968, Gillain's company produced Total Journal, another advertising magazine, distributed through Total gas stations. Editors for this publication were Jean-Claude Mézières and Pierre Christin, the authors of 'Valérian', and contributors were Brétecher, Gotlib, Mandryka, Giraud and Jijé.