While Charles IX was still alive and feeding the flames of war against the French Protestants, his brother, Hercule, (next in line for the throne who also took the name of Francis) passed away.
When Charles IX passed away Catherine’s last son, Henry III, had already been crowned King of Poland and Austria.
His mother asked him to come home because his country needed him. He abdicated the Polish throne to rule France.
Things get very interesting after this point because the Guises did not want to give up their influence in the court.
This gave rise to the formation of The Catholic League, the demise of Henry III and the ascendancy of Henry III of Navarre (Henry IV of France).