The history of early mediaeval Wales is bedevilled by the lack of contemporary written and pictorial sources. As a result there are long periods of time where we know little or nothing about large areas of Wales.
This problem is compounded by the tendency of some of the earlier modern historians to retrospectively apply evidence from later mediaeval. Wales e.g. the Laws of Hywel Dda, or Hywel the Good, (who died AD 949) which first occur in thirteenth century copies of twelfth century manuscripts. While most historians agree that these laws must contain an element of earlier material, it is difficult to assess the precise amount. It is virtually impossible to tell which laws are twelfth century and which are earlier.
There was also a inclination among some earlier historians to apply the contemporary evidence from other Celtic nations to the Welsh, wrongly believing that there was a 'common' Celtic society sharing the same attitudes and institutions. The Celtic peoples considered themselves to be individual nations, and not part of some greater 'Celtic' nation. The Welsh thought of themselves as Cymry or Britons, the Irish thought of themselves as Gael, etc.. But ultimately, the meaning meant the same, 'us', or 'the people'.
Fortunately we have good evidence for the continuity of certain practices in Wales, e.g. the 'multiple estates' system. This is only fully recorded in twelfth century law tracts, yet there is evidence in the Llandaff charters which suggests that a similar practice occurred in south-east Wales during the eighth century. Likewise there is much about life in twelfth century Wales recorded by the monk, Giraldus Cambrensis, which may also be applied to the eleventh and earlier centuries.
There is less evidence for the Welsh social structure than that in Ireland or Brittany; yet this is still greater than the surviving evidence for Scotland, Cornwall and the Isle of Man. Only four classes of Welsh society can be identified from surviving documents: kings, nobles, tenant peasants and slaves. While it is possible that a fifth class of free landholding peasants also existed, there is no surviving evidence of this.
Kings (OW. 'Rhi' pl. 'Rhiau' or 'Teyrn' pl. 'Teyrnedd') claimed their right to rule by descent. Kingship was most frequently passed from father to son or brother to brother. The annals and genealogies stress 'dynastic dominance and dynastic continuity", sons were expected to succeed fathers. In practice kingdoms were sometimes shared, and occasionally quarrelled over between brothers or uncle and nephew. Occasionally there were quarrels between father and son.
Wales unlike Scotland and Brittany, was never a single united kingdom. It was composed of several separate kingdoms each traditionally ruled by its own dynasty. These were, by the ninth century; Gwynedd, Powys, Ceredigion, Dyfed and Glywysing (also known as Morgannwg after Morgan Hen literally 'Morgan the Old' c.930 - 74, modern Glamorgan). Within some of these there also seem to have been sub-kingdoms, ruled either by members of the same dynasty, or by unrelated kings of unknown origin, e.g. Gwent, Ergyng and Builth in Glywysing. All these kingdoms could be dominated by one or more kings, or even none at all. It was also possible for one king to rule more than one kingdom (from the ninth century until 1063 the kings of Gwynedd also ruled Powys), or for conquered kingdoms to be divided between a king's sons. On the death of Rhodri Mawr (or Rhodri the Great\Large), in 878AD his son Anarwd retained his father's kingdoms of Gwynedd and Powys, while his son Cadell ruled the newly conquered kingdom of Dyfed.
Kings were expected to be rulers, law givers, judges, leaders of the war band and protector of the Church and people. Their income appears to have been largely derived from their own personal estates, but there is some evidence from Glywysing that by the eighth century kings were establishing control over their nobles by exacting a land tax on estates. This took the form of a yearly render, usually of food, known as 'gwestfa'. According to twelfth century law tracts this practice had become more widespread.
Nobles (OW. 'Uchelwr' pl. 'Uchelwyr' or 'Breyr' pl. 'Brehyron' ) were the free landowners in Wales, and as such formed the aristocracy. There is evidence for their existence from the sixth century. They owed their position to their hereditary freedom to own land, and the power this gave them over their tenant farmers and slaves. They owed no service, rent or due to the king other than the 'gwestfa', repair of bridges and roads on their lands, and service in war. Many aspects here are almost identical to Anglo-Saxon law and expectations. The king might choose to ignore or remit these as he wished, or a noble might be powerful enough to resist his monarch's attempts to enforce them.
Nobles owned their land in the form of large estates. These could be grouped together to form multiple estates, or spread over a wider area. They could dispose of their lands as they wished, provided interested parties such as heirs or kindred were in agreement, although for a while kings tried to control land grants to the Church. Nobles could act as foster parents to the sons of kings and other nobles' sons. They could also serve on the king's council (OW. 'Degion') as a 'Gwr Da' or good man, acting as royal officers and advisors. The Degion could even govern the kingdom in the king's absence. A noble's son might serve in the king's warband for a few years, receiving hospitality, arms, treasure and even land in return for his service, before returning to manage the estates.
Peasants (OW. 'Aillt' pl. 'Eillt') were bondsmen, the unfree tenant land holders of noble landlords. They were tied to the land and could not leave it without their lord's permission, and they accompanied the land if it was sold or granted away.
They lived in separate settlements known as a 'tref' pl 'trefi' with the slaves who were under them. They worked the land, returning a food rent to their landlord and a twice yearly direct payment to the king of 'dawnbwyd'; they did not do labour services. Peasants (and Nobles) could fall into slavery through economic reasons, as a penance, a criminal punishment, or as captives. There is no evidence that peasants could rise to the nobility and by the twelfth century their position was being eroded.
Peasants could do service in war. The twelfth century law tracts suggest the king could enforce them to do four days war service a year. They had to provide their own food and presumably their own arms as well. The late eleventh century work, the 'Life of St Cadog' by Lifris mentions the slaughter of a peasant army in a dispute between two landlords.
Slaves (OW 'Caeth' pl 'Caethion' ) were primarily agricultural labourers, born into slavery and tied to the land. They were regarded as important property, however there is evidence that they were often undernourished and underfed. Slavery could be imposed as a religious penance or a criminal punishment. In their spare time both slaves and peasants could specialise in craft activities like smithying and shoemaking. Slaves were allowed to own goods and save money; they could and did, where possible, buy their freedom. There is no evidence that they were expected to arm themselves and fight, although it is not unthinkable that a slave employed as a door warden would be armed.
Unlike most of Western Europe, slavery in Wales did not decline during the period. This must be partly due to the harshness of the climate and the poor quality of most of the land, which created a great demand for labour. There is no evidence that a shortage of land occurred until the twelfth century when kings began designating certain areas as their hunting grounds rather than loose more land to the plough. Prior to that it was common to find records of the foundation of new settlements and associated land clearances for arable fields. Before the twelfth century the major barrier to agricultural expansion was the shortage of labour. This was clearly stated in several manuscripts. Lifris bemoans the slaughter of the peasant army, chiefly because of the loss of labour it caused. It would have been the action of a foolish man to risk losing slaves in war. Land was useless without labour, whoever controlled it could work the land. As a result the servile population was maintained and the peasant population witnessed a decline in their position between the eighth and twelfth centuries.