§ 1. a.d. 1137. King Gruffydd ab Cynan left many surviving sons, who severally inherited certain portions of his territories. Owen, the eldest, succeeded him in the provincial sovereignty of Gwynedd, and in the hereditary claim to paramount dominion over Powys and Deheubarth. From the date of his accession, however, the native chroniclers cease to apply the term Brenhin to their kings, and substitute the term Twywysog; and district sovereigns, thenceforth, they usually style Arglwydd, after the manner of the Normans, although the English and Norman chroniclers continue to apply the word regulus to every Welsh sovereign.

The changes in the ownership of land, which took place throughout every family at the decease of each proprietor, have rendered it almost impossible to ascertain which territories were held in successive reigns by the brothers and sons of late and then present sovereigns, and the Norman usurpations and lands regained from foreign foes, or won from each other by the native princes, tend to complicate the difficulty still more. Nevertheless, attention to the incidental mention made of cantref and cwmwd will often enable the careful student to catch at least a fragmentary clue to the localities and boundaries of family properties in successive ages.