How did the Guise family gain influence during the reign of Francis II?

During the reign of Francis II (1559–1560), the House of Guise gained significant influence by exploiting the young king’s weak will and sickly demeanor, which made him highly susceptible to manipulation. Upon Francis II's accession, the Guise brothers—François, 2nd Duke de Guise, and Charles, Cardinal de Lorraine—effectively became the heads of government.123

The brothers replaced the constable Anne de Montmorency as the primary power brokers in the royal household. They consolidated their authority by positioning themselves as the defenders of Roman Catholicism, supported by Spain and the papacy, and used their position to persecute Huguenots. While the Bourbon family held a stronger legal claim to advise the king as princes of the blood, they lacked the political cohesion and influence the Guises had secured during this period. This monopolization of royal authority by the Guises became a central point of contention for Catherine de’ Medici, who viewed their extremist policies as a threat to the independence of the crown.245