The leader of the ongoing crusade, Simon de Montfort, 5th Earl of Leicester, who was at that time at the height of his power, had Petronilla in 1216 married to his own son Guy.
In total Petronilla had three children, two from her third marriage and one by her fifth marriage: With Guy de Monfort she had two daughters: With Boson of Mastas she had one daughter: Near the end of her life, the Countess Petronilla relinquished the government of Bigorre to her brother-in-law, Simon de Montfort, Earl of Leicester and governor of Guyenne.
To prevent Guyenne and Gascony from rebelling, Henry III of England recalled Simon de Montfort and appointed John Grailly in his place.
Petronilla's grandson was Eschivat de Chabanais who had succeeded his mother Alix without protest, but made the mistake of keeping land that Martha had in Bigorre.
Martha's husband Gaston VII of Béarn then invaded the county, forcing Eschivat to defend it, seeking the assistance of Prince Edward of England and the alliance of Count Roger IV of Foix.
In 1258, war resumed in the region and Eschivat agreed to temporarily surrender the County of Bigorre to Simon de Montfort, this time to end the conflict.
Soon after, Simon de Montfort rebelled against King Henry III, and Eschivat helped Gaston VII regain Bigorre.
In 1407, it belonged to Bernard VII of Armagnac, who sold it that year to John I, Count of Foix, (a descendant of Petronilla through Martha).