Complex sentence: Fulk of Jerusalem then chose Raymond of Poitiers, a younger son of William IX, Duke of Aquitaine, as future husband for Constance, Alice nor Roger II of Sicily were to learn of this.
Split into simpler sentences: Fulk of Jerusalem then chose Raymond of Poitiers, a younger son of William IX, Duke of Aquitaine, as future husband for Constance. Neither Alice nor Roger II of Sicily were to learn of this.