The Life of Saint Francis de Sales

We trace to Life of Saint Francis de Sales
What were his parents thinking about for this, their first baby?
Would he continue in the House of Savoie, taking care of the land, his heritage?
Would Francis Bonaventure follow in the footsteps of his namesakes?
Although we read that both parents were traditional Catholics, could they have had any idea what they were doing when they gave such powerful names to their newborn?