Complex sentence: One was Conduché and the other was his niece Virginie Gavalda, both of whom were called nieces and sent by Father Gavalda to attend the Sisters of Notre Dame in Saint Julien d'Empare to round out their education.
Split into simpler sentences: One was Conduché and the other was Virginie Gavalda, both of whom were called nieces. The young women were sent by Father Gavalda to attend the Sisters of Notre Dame in Saint Julien d'Empare to round out their education.