Piron lists twelve of them… with a majority of men (9). Five are from the Academy of Ghent, and three from the Academy of Brussels. Only Jean Mortier, born in 1929, signs under the pseudonym JEM. Four first names begin with the letter A. The artists listed below primarily sign their work as Mortier, and you’ll need to pay close attention not to confuse them, even if the stylistic differences in their approaches weren’t already clear enough.
In chronological order
Emile Mortier, born in Brussels in 1892—died in 1977. Painter, sculptor. Studied at the Brussels Academy; father of Marcel Mortier. Painted seascapes, still lifes, and compositions featuring one or more figures.
Antoine Mortier, born in Brussels–Saint-Gilles on October 2, 1908; died on January 26, 1999. Painter, draftsman, sculptor. Self-taught in painting, he took courses in casting and decorative sculpture at the Academies of Saint-Josse and Brussels. He held various jobs beginning in his teens, including as a set painter, furrier, and chorus member at the Théâtre Royal de la Monnaie and the Alhambra, as well as a picture framer. Member of the Jeune Peinture Belge group (March–November 1946). His entire body of work embodies the spirit of abstract expressionism and lyrical non-figuration.
Antoon Mortier, born in Ghent in 1919. Painter, draftsman, illustrator. A student at the Ghent Academy and the Saint-Luc Institute in Schaerbeek. His expressionist-style body of work depicts night owls and outsiders in pieces that are primarily in black and white. He lives and works in France.
Marcel Mortier, born in Brussels in 1919 and died in France in 2009. Painter, musician, son of Emile Mortier. He is known for his landscapes of Provence and Flanders, his still lifes, his cityscapes, and his circus scenes, all rendered in a synthetic style with intimate color palettes.
With that said, you’ll need to be extra vigilant when analyzing the signature itself, since people with the same name aren’t necessarily forgers—and vice versa. Analyzing the signature and style remains the best approach, as sellers do not hesitate to bolster their offers with one biographical detail or another about the most highly valued artist.