His wife , Clothilde Breal , was of Jewish origin and her cousin , Lise Bloch , was married to Leon Blum , the first Jew to become President du Conseil or Prime Minister in France . Moreover his wife , Clothilde Breal , daughter of the linguist Michel Breal , was of Jewish origin and Clothilde Breal 's cousin , Lise Bloch , was married to LÃ on Blum , the first Jew to become President du Conseil or Prime Minister in France .