He grew up in a very close family atmosphere at Sedan where he also received his academic education. One of his teachers was Dumoulin, a strict Calvinist. It was his uncle, the Duc de Bouillon, who introduced him to diplomacy in 1612 and whom he accompanied to London.
Here his uncle opened marriage negotiations for a cousin, the young Elector Palatine, who sought the hand of King James I's daughter. On the way home they went via Holland to meet his Dutch uncles, Maurits and Frederik Hendrik.
At first the French King objected to Henri's marriage to his cousin, Marie de La Tour, but preferred it to an allicance with a German Protestant family. Their marriage took place on the 19 March 1619.
Around this time Louis XIII forced the return of Catholicism in Navarre, which frightened the Huguenots in all of France as he confiscated the Protestants churches, schools and even cemeteries. Also children were taken from their parents, and women and children were forced to attend Mass. In shock, the leading Huguenots met and on 10 May 1621 a declaration threatened France with civil war. Shortly  after this, Louis XIII called Henri to his presence and, when he went, his wife returned to her family. However, after the treaty of Montpensier she returned to her husband.
Henri had become a general for the king against the Protestants. And while besieging La Rochelle, in the presence of the Court on 18 August 1628, he became a Roman Catholic. This caused a rift between him and his Protestant family and especially with his mother, who left for Chateau Renard where she died in October 1631.
After having taken his son to make him also a Catholic, he gave his son to the Jesuits for further education. He was furious when his son escaped a few years later to Protestant relatives in The Netherlands. Many years later again, his son returned to France with a Protestant bride. However, his son's return did not last as, after imprisonment by Cardinal Mazarin, his son returned to The Netherlands.
Marie, his own wife, had been the stronger of the two and the Duchy of Thouars remained Protestant, even if he, their Duke, was a Roman Catholic. Louis XIV and Cardinal Mazarin remained quiet until Marie died, but a month later he received a complaint from the King about
Protestant services being held in Thouars. Also, Louis XIV would not allow him to let his grandchildren return to their parents in The Netherlands.
Henri tried to convert his grandchildren, Charlotte Amelie and Charles Belgique Hollande, even threatening to lock his granddaughter up in a Catholic convent. However, his brother-in-law, Vicomte Turenne, warned the children's parents in The Netherlands and the children's mother, Emilie, hurried to France. Arriving at five in the morning, she begged her father-in-law to allow her to take her children back with her. Weak-willed, Henri would say neither yes nor no, and it took Emilie two hours of pleading before he finally consented.
In his later years he would see the return to France and to Catholicism of his son and grandson. He survived his son and when he died, 21 January 1674, it was his grandson who became the next Duc de Thouars.
 

Source: Leo van de Pas