He permanently reunited the kingdoms on the death of his father and passed them to his own son, Alfonso X.  Alfonso X's eldest son Ferdinand died in 1275 leaving two sons, but the king's second son Sancho claimed to be the new heir. The king preferred Ferdinand's sons, but the nobility supported Sancho and a civil war began. The descendants of Ferdinand form the House of la Cerda. Alfonso X died in 1284 and finally his second son succeeded him, as Sancho IV. The grandson of Sancho IV, i.e. Alfonso XI, had legitimate son Peter of Castile and some illegitimate sons: Henry, Fadrique, etc. Henry attacked Peter with a host of soldiers of fortune in 1366. The Castilian Civil War followed: Peter was besieged at the fortress of Montiel. During the negotiations, Peter entered the tent of Henry's envoy, where Henry, which was hidden there, attacked him and killed him. Peter had no legitimate sons, and Henry became the new king as Henry II and was the founder of the House of Trastámara. His brother Fadrique became the founder of the House of Enríquez.