arriterre asked me to look up Philippe Hurepel, the son of Philippe II of France and Agnes of Meran. Here's what I found, using The Norman Frontier in the Twelfth and Early Thirteenth Centuries by Daniel Power, The Empire and the Papacy, 918-1273 by T.F. Tout, The Government of Philip Augustus by John Baldwin, and The Routledge Companion to Medieval Warfare by Jim Bradbury.
Philippe Hurepel was born July 1201, the second son of Philippe Auguste, born to his controversial union with Agnes of Meran. They already had one daughter together, Marie, and Philippe Auguste's heir was his surviving son by his first wife, the future Louis VIII. Agnes died at Poissy soon after delivering Philippe Hurepel. She was buried with great ceremony at St. Corentin at Mantes.
Philippe Hurepel was legitimated by Pope Innocent III. According to Rigord, this was met with much resistance outside the royal family.
Renaud de Dammartin was one of Philippe Auguste's more rebellious barons. He had divorced his first wife, Philippe's cousin Marie of Chatillon, and abducted and married Countess Ida of Boulogne (apparently with her consent, if Lambert of Ardres is to be believed). Renaud and Ida then tried to use her previous relationship with Arnold II of Guines to lure Arnold to them and capture him. Then Renaud got involved in a war with the bishop of Beauvais, Philippe's cousin. He was also accused of numerous other crimes, such as parading his concubines in public and attacking the Church. Philippe ordered Renaud to surrender Mortain. When Renaud dragged his feet, Philippe seized the county and granted it in 1222/3 to his own son, Philippe Hurepel, who married Renaud's daughter and heiress, Matilda. Renaud was exiled and went to John's camp in 1212. He fought against Philippe at Bouvines and was captured. In 1217, Renaud committed suicide in captivity, and Boulogne went to Philippe Hurepel and Matilda.
Philippe Hurepel and Matilda had one daughter, Jeanne. Jeanne married Gauthier of Chatillon, heir of the countess of Nevers, but they had no children and she died in 1252. Philippe Hurepel's sister Marie married first Philippe I of Namur, and then Henry I of Brabant, and had children from the second marriage.
After the death of Louis VIII, Philippe Hurepel was one of the leaders of the coalition against the regency of Louis' widow, Blanche of Castile. He was joined by Pierre Mauclerc of Brittany and Raymond VII of Toulouse (the son of Joan, Richard and John's sister). They demanded that royal authority be granted to Philippe Hurepel and that Blanche return to Spain. They did drive her to the protection of Thibault IV of Champagne, but were never able to break her hold.
Philippe Hurepel died in 1234 and was one of the few Capetians never to wear a crown to be buried in St. Denis. His wife Matilda remarried to Alfonso, son of Sancho II of Portugal, who repudiated her in 1247 when he became king of Portugal himself. Matilda died in 1258. Louis IX granted Aumale to Matilda's cousin, Jeanne de Dammartin, the wife of King Fernando III of Castile (and the mother of Leonor who married Edward I of England). Boulogne was given to Matilda's other cousin, Adelaide of Brabant.