Gaston of Orléans, brother of Louis XIII, his revolts and loss of the regency
In royal history I like the heroes of the supporting roles. Gaston d'Orléans (1608-1660), for example, who was called the only brother of the king, Louis XIII. In fact Marie de' Medici had another son, Nicolas, or the prince without a name, who lived for four years.
Gaston is that very Duke of Orléans from "The Three Musketeers". The favourite son of a raving queen and for a long time the first in line to the throne after Louis, he rose up again and again against the king's authority and backed every revolt and disturbance, knowing full well that Louis would not shed royal blood. But in the end he overplayed his hand and was stripped of the right to become regent for the heir in the event of the king's death. Gaston lived in the splendid château of Blois, and I wrote something about him here: https://theparnassian.com/postroennyi-v-xv-veke-familnyi-zamok-gertsogov-orleanskikh-shato-de-blua-byl-rezidentsiei-liudovika-xii-i-vposledstvii-ego-ziatia-frantsiska-i/