King Louis VI the Fat (1081-1137, reigned 1108-1137) had a total of nine children in his life, numbering seven sons and two daughters. Among those children, his favorite was his eldest son Philip, born in 1116. Philip was associated to the crown as co-king in 1129, which seems to have gotten him way out of his head as he started acting like a spoiled brat.
Young philip however never had a chance to succeed his father : he accidentically killed himself by falling from his horse in 1131. With his death, his younger brother, Louis the Younger, who should have followed an ecclesiastical career, became heir to the throne and succeeded his father to become Louis VII of France.
Let's suppose young Philip doesn't kill himself in 1131. He would thus remain co-king with his father until 1137 where he would become king Philip II of France and start his personnal reign. He would also go on a crusade because he had dream to visit Jerusalem and the tomb of the Christ.
During Louis VI's reign, the King of France had strike a friendship to William X, Duke of Aquitaine. This ultimately resulted in the arranged marriage of Eleanor, William X's only daughter, to Louis VI's heir, who was Louis VII OTL. However, if Philip survives, I think it is likely for him to marry Eleanor.
The consequences of this could be massive : if Eleanor is happy with Philip, that means she won't marry Henry Plantagenêt and this will butterfly away Richard Lionheart and John Lackland. This also means Aquitaine becomes part of the royal domain and is likely to increase royal control over France.
Question : who will Henry Plantagenêt marry in that case?
Another question is, how far could Louis the Younger go in the Chuch? Two of his brother made a pretty decent carreer in the church OTL : his younger brother Henry (1121-1175) became Archbishop of Reims and another of his brother, Philip (1125-1161) became Bishop of Paris.
Thoughts?