His son Roger avenged him and married Azalaïs in 1171, daughter of Raymond V.
The Cathar sympathies of his son Raymond-Roger gave the barons of the north who started a crusade in answer to the call of Pope Innocent III, a pretext to take Béziers and Carcassonne, where the young Viscount had withdrawn in 1209. Made a prisoner, the Viscount died on 10 november 1209 in the jails of Carcassonne, of dysentery according to some, assassinated according to others.
His son lived in exile at the court of the King of Aragon but in 1240 tried, with the help of other "faidit" lords (dispossessed), to reconquer the lands of his fathers, but failed before the walls of Carcassonne and had to go back into exile.
After the failure of reconquest, the population of Carcassonne was exiled, and could come back only seven years later. The inhabitants then founded the Lower Town on the other side of the Aude river.
The last Trencavel disappeared from our history when he decided to go at his turn on Crusade in Palestine at the end of the 13th century...