Fr. Nicholas has an interesting post on King Charles Emanuel IV of Sardinia, who in 1775 married Louis XVI's sister Clothilde. (Charles Emanuel's sisters were married to Louis' brothers.)
Charles Emanuel was raised in a very religious - almost ascetic - household. His principal tutors were Count Roberto Giuseppe Malines de Bruino and the Barnabite priest (later cardinal) Don Giacinto Sigismondo Gerdil. He studied military science under the noted engineer Alessandro Vittorio Papacino d'Antoni. Charles Emanuel had a weak constitution and was frequently ill. He suffered from violent nervous convulsions; it is possible that he had epilepsy.Share
For the first part of his life Charles Emanuel's main residence was at the Palazzo Reale in Turin. In the summer his family retired to the castle at Moncalieri on the outskirts of Turin or to La Veneria near the town of Bra some thirty kilometres south of Turin.
In 1773 Charles Emanuel's father succeeded to the throne of Sardinia. From this point serious consideration began to be given to Charles Emanuel's marriage which would be arranged for political reasons. Two of Charles Emanuel's sisters were married to the younger brothers of King Louis XVI of France (Giuseppina to the Comte de Provence, later King Louis XVIII, and Maria Teresa to the Comte d'Artois, later King Charles X). Charles Emanuel's sister Giuseppina suggested a match with her sister-in-law Princess Marie-Clothilde of France, daughter of the late Dauphin Louis and of his wife, Princess Maria Josefa of Saxony. After two years of negotiations Charles Emanuel (represented by the Comte de Provence) was married to Marie-Clothilde by proxy on August 21, 1775 at the Palace of Versailles.
Charles Emanuel and his new wife met for the first time on September 6, 1775, when they renewed their marriage vows in the Chapel Royal at Les Echelles, Savoy. In spite of the political reasons for the union, the couple were well-matched; they shared a profound attachment to the Catholic faith. The fact that they were not blessed with children was treated by them as the will of God to which they should resign themselves. After seven years of married life, they chose to live together as brother and sister.
Charles Emanuel was deeply troubled by the French Revolution whose effects were being felt throughout western Europe. In 1793 his brother-in-law King Louis XVI was executed. The following year his sister-in-law Queen Marie Antoinette met the same fate and the armies of the French Republic stormed into his father's dominions. Charles Emanuel took solace in his faith. In 1794 he became a member of the Third Order of Saint Dominic, taking the name Charles Emanuel of St. Hyacinth. (Read entire article)