Firmin Louis Joseph Mengeot born 16/03/1878 Farciennes, Belgium, married in Brussels 30 June 1906 to Camilla Eugenia Alina Maria Simon (a Belgian Simon, she was born in Antwerp 18 July 1878, daughter of Camille Charles Leopold Simon born 1843 Bouillon, Belgium and Celina Sophia Maria Lair, born 1849 Brussels). Firmin and Camilla had a daughter Yvonne Gabrielle Suzanne Mengeot born 29 November 1902 Namur, Namur, Belgium
On the 1931 Montreuil census (reply #13), Leonie Adolphine Houdret and Firmin Louis Joseph Mengeot both lived in the rue Parmentier n° 71, but in different households.
On the 1936 Paris census, Leonie Houdret lives in the rue d’Avron n° 144, “chef” (head) of the household, the only other member of the household is Firmin Mengeot, he is “A” of Leonie. (A ? = ami ?)
Firmin Mengeot was one of the witnesses on Isabella Simon’s marriage (x 1935)
Leonie Houdret still lived at rue d’Avron n° 144 when she died (+1959)
Firmin Mengeot died at home rue d’Avron n° 144 + 27 March 1961
http://www.rootschat.com/links/01ppx/burial register cimetière parisien de Pantin, Bobigny, Seine-Saint-Denis
http://www.rootschat.com/links/01ppy/So Leonie Houdret and Firmin Mengeot knew each other for a long time. There’s some info on Ancestry for Firmin Louis Joseph Mengeot, Camille Eugenie Aline Marie Simon and Yvonne Gabrielle Suzanne Mengeot. I don’t know exactly what (I don’t have a subscription), but maybe the person who put this online knows something about your Simon’s.