Orphaned at a young age, Félix was the son of Herménégilde Sirois and Édith Martin. He became a protégé of the Sisters of Saint-Basile, in 1874, and was entrusted to the Religious Hospitallers of Montreal who then had an orphanage for boys. Félix also studied with the Jesuits before undertaking medical studies. In 1888, the young Félix Sirois received the title Maître ès Chirurgie at the Victoria College of Medicine in Montreal. He practised in Saint-Basile and Fort Kent. His marriage to Catherine Martin from Saint-Basile was celebrated on February 9, 1891, the day of the fiftieth marriage anniversary of his grandparents, Mr. and Mrs. Urbain Martin, who were retired at Hôtel-Dieu.