Original: 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 Léon Blum, the first Jew to become President du Conseil or Prime Minister in France.
Simplified: 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.