In the seventh century the main division in southern Wales was between Dyfed (derived from the tribal name Demetai, recorded by Ptolemy) in the south-west and Gwent (from Venta Silurum, Caer-went) in the south-east, while Ergyng (from Ariconium), to the north of Gwent, had its own kings. By the ninth century, however, Ergyng was dependent on Gwent, and Dyfed and Gwent were no longer adjacent: the old western part of Gwent (Glamorgan), now known as Glywysing from the legendary ancestor Glywys, and the eastern parts of Dyfed – Ystrad Tywi, Gŵyr (Gower), and Cydweli (Kidwelly) – were sometimes named as separate regions. In the 880s, as we know from Asser, Glywysing and Gwent were independent kingdoms, ruled respectively by Hywel ap Rhys and by Brochfael and Ffernfael, sons of Meurig, but from ca 893 Hywel's son Owain may have ruled both kingdoms, being described as ‘king of the people of Gwent’ in the D-text of the Anglo-Saxon Chronicle for 927. Owain's son, Morgan ab Owain (ob. 974), later remembered as Morgan Hen or Morgan Mawr, seems to have inherited this role, while allowing his brothers to be sub-kings in Gower and western Glywysing, areas disputed with Dyfed in the second half of the tenth century. His name probably survived in the name of the more restricted kingdom of Morgannwg (Glamorgan), the name which had superseded Glywysing by ca 1000. Gwent, by contrast, fell into the hands of a new dynasty, that of Rhydderch ab Iestyn (ob. 1033), and his sons and grandsons are prominent in the south-east in the latest charters in the Book of Llandaf.

While the identity and relationships of the kings mentioned in the later parts of LL are mostly straightforward, the earlier kings present many problems, not least because of ambiguities and disagreements in the extant south-eastern genealogies. These genealogies will be discussed in chronological order of attestation, starting with the Harley genealogies, before turning to LL itself in order to see how far the genealogies agree with the charters of Sequences i and ii, and the earlier part of Sequence iii.