The whole process of trying to enumerate and explain the various kingdoms of Wales that existed between the 6th and 13th centuries is rather complicated, mainly for the following two reasons.
(1) Welsh kingdoms were essentially fluid and unstable constructs that relied upon the personal authority of whoever was recognised as king at the time.
The kingdoms were really no more than aggregations of commotes that recognised some particular individual as king. Each king would possess a power base derived from his authority as tywysog of the commutes in his possession, but ultimately his power depended on the support he had from the other tywysogion within the kingdom. Such power naturally waxed or waned in accordance with the personal qualities of each king. There were no real political or administrative institutions attached to the kingdom above the level of the commote and therefore nothing to sustain anything remotely approaching a nation state.
Which was basically a recipe for constant intrigue and internecine strife and a certain vagueness over borders.
(2) The presumption against primogeniture.
The medieval Welsh were an egalitarian lot, (unlike
for example, the English who were strict adherents of
primogeniture) and there was a presumption that every
male heir had an equal right to inherit.
This meant that whenever a ruler died, his territories
were often divided up between his sons (and quite
often the sons would have a good argument and a minor
civil war over who got what).
Also since Welsh Law also recognised the inheritance rights
of illegitimate children, this could sometimes get
quite silly; the kingdom of Deheubarth eventually disappeared in
the 12th century when the last king died leaving 18
As a result of the both the above, the kingdoms were forever dividing, being reformed, dividing again, taking over neighbouring kingdoms, changing their names, getting occupied by the Anglo-Saxons or Normans, revolting, getting re-occupied, until the Welsh eventually accepted the inevitable and gave up armed resistance at the end of the 13th century.
It should also be remembered that for much of this period there is little in the way of surviving records. It is therefore difficult, particularly for the first three or four centuries or so, to have any clear idea of what is going on at all.
But with above qualifications, these are the kingdoms that existed within the confines of Wales between the fifth and thirteenth centuries anno domini;
- Brycheiniog - south central Wales, sandwiched between Powys and Glywysing/Morgannwg
- Buellt - central Wales, roughly north west of Brycheiniog
- Ceredigion - west central Wales, on the coast facing Ireland
- Cynllibiwg - central Wales, approximately northern Radnorshire
- Deheubarth - from around 920 onwards, the creation of Hywel Dda, a merger of Dyfed and Seisyllwg
- Dyfed - located in south west Wales, roughly modern Pembrokeshire plus Ystrad Tywi
- Ergyng - to the east of Gwent, absorbed into Mercia sometime after the seventh century
- Glywysing - south east Wales, between the rivers Tawe and
- Usk, along the coast with Ystrad Tywi to the west, Gwent to the east and Brycheiniog to the north
- Gwent - south east Wales, between the Usk and the Wye, that is Glywysing/Morgannwg and Ergyng
- Gwynedd - north west Wales including the island of Mon or Anglesey
- Morgannwg - as Glywysing was renamed after around 950
- Powys - east central Wales, spent most of teh tenth century under the rule of Gwynedd, later split into Powys Wenwynen and Powys Fadog
- Rheinwg - what Dyfed was called after it lost control of Ystrad Tywi
- Seisyllwg - the name bestowed upon Cerdigion after gaining Ystrad Tywi from Dyfed