 After the death of his brother William VII, around 1172, Gui served jointly with John of Montlaur, bishop of Maguelonne, as guardian of his nephews, particularly of William VIII who had inherited the lordship.In this capacity Gui and John attended the conference at Mezouls in 1174 at which Raymond V of Toulouse and Alfonso II of Aragon negotiated an agreement with the young William VIII.In October 1174 Gui was at Alfonso II's court at Lerida.