1658 appears to have been the key year in which Philippe's sexuality became well defined.
Phillippe I (aka Monsieur) certainly did make his first contacts that year with Philippe de Lorraine (aka the Chevalier de Lorraine), the male lover with whom he would establish the closest emotional attachment throughout his life.
Among the lovers, one man stands out, Philip of Lorraine-Armagnac, the never-married Chevalier de Lorraine, who was described as "insinuating, brutal and devoid of scruple". As a member of the House of Guise, ranking as a prince étranger, Philippe could keep him near while at court and promote him within his own household without initially evoking scandal or offending sensibilities.
Chevalier de Lorraine was three years younger than Monsieur. Insinuating, brutal and devoid of scruple, he was the great love of the life of Monsieur. He was also the worst enemy of the latter's two wives. As greedy as a vulture, this cadet of the French branch of the House of Lorraine had, by the end of the 1650s, hooked Monsieur like a harpooned whale. The young prince loved him with a passion that worried Madame Henrietta and the court bishop, Cosnac, but it was plain to the King that, thanks to the attractive face and sharp mind of the good-looking cavalier, he would have his way with his brother.
Monsieur married Henriette Anne at the Palais-Royal in 1661. Monsieur openly flaunted his affairs at court, especially his long term lover Lorraine.
Monsieur even told Henriette Anne that he could not love her without Lorraine's permission. Monsieur's first marriage was not a happy one. In January 1670, his wife prevailed upon the King to imprison the chevalier, first near Lyon, then in the Mediterranean island-fortress of the Château d'If, and finally he was banished to Rome. But by February, Monsieur's protests and pleas persuaded the King to restore him to his brother's entourage.
In 1670, Henriette Anne died suddenly at Saint-Cloud, and it was suspected that Lorraine had been the murderer, even though the autopsy performed reported that Henrietta-Anne had died of peritonitis caused by a perforated ulcer.
In 1682, Lorraine was exiled again, having been accused of seducing the young Count of Vermandois (son of Louis XIV and Louise de La Vallière) with his set (including the Prince of Conti) and began practising le vice italien (the contemporary appellation for homosexuality).
Having been allowed to return to court, he was then blamed for helping to instigate the marriage between Philippe d'Orléans, duc de Chartres and Mademoiselle de Blois in 1692. Chartres was the son of Monsieur and his second wife Elizabeth Charlotte of the Palatinate, who did not get on with Lorraine at all and merely "tolerated his existence". Monsieur and Elizabeth Charlotte married in 1671.
According to Henriette Anne, Elizabeth Charlotte and Saint-Simon, Monsieur was frequently manipulated by Lorraine. Monsieur died in 1701; by the end of his own life, he had lost his collection of furniture at the Palais-Royal (much of which was from the Palatinate) and the money from the abbey, but he did reconcile with Elizabeth-Charlotte.