Complex sentence: Unlike the older children of Louis XV (including Adélaïde, just one year her senior), Victoire was not raised at the Palace of Versailles, but sent to live at the Abbey of Fontevraud.
Split into simpler sentences: Unlike the older children of Louis XV (including Adélaïde, just one year her senior), Victoire was not raised at the Palace of Versailles. Rather, she was sent to live at the Abbey of Fontevraud.