From "The Matter of Wales: Epic Views of a Small Country" by Jan Morris, ISBN 0-19-504221-2, page 59:
In the early years of Wales, there were as many as 18 separate princedoms within the 8,000 square miles of Wales, largely because the Welsh law of portion, gavelkind, divided inheritances equally among all a man's sons, and so fragmented kingdoms as well as farms. They often fought against each other, besides being engaged in interminable warfare with their enemies. Between 949 and 1045, according to the 13th century Brut y Tywysogyn, the Chronicle of Princes, 35 of their rulers died by violence and 4 more were forcibly blinded.
page 60:
Gradually the multitudinous little princedoms were consolidated into greater wholes, and four major Welsh kingdoms emerged: Gwynedd in the north, Powys in the east, Deheubarth and Morgannwg in the south. They generally came into being peacefully, by policy and marriage, and though they were often at odds with each other, they seldom went to war. Several great rulers, Rhodri Mawr of Powys, Hywel Dda of Deheubarth and the two Llywelyns of Gwynedd, each briefly succeeded in uniting almost all Wales under one aegis.

From "The Matter of Wales: Epic Views of a Small Country" by Jan Morris, ISBN 0-19-504221-2, page 67:
Out of the Welsh heartland leader after leader sprang to defy the English power, culminating in the two Llywelyns of Gwynedd, the Great and the Last, who made a virtual federation of independent Wales, and were to personify forever the spirit of the resistance. A running war that had lasted on and off through 8 English reigns, from William the Conqueror to King John, had never achieved serenity for the English in Wales; it was only in the reign of King Edward I of England that a soldier in the royal service killed Llywelyn ap Gruffydd of Gwynedd, and so symbolically ended the Independence of the Welsh.
Actually resistance continued even after the death of this charismatic prince, but it is the killing of Llywelyn Olaf, the Last, near the hamlet of Cilmeri in Powys, that has remained in Welsh minds the fatal fact. A big stone of rough-hewn granite beside the road marks the place where he is said to have died, on a bitter snowy day in the winter of 1282.
When Henry III was on the throne of England, Llywelyn was recognized even in London as Prince of Wales, and in return, he acknowledged the suzerainty of the English Crown. Under Edward I matters changed. First Llywelyn refused to pay tribute, then he insisted on building a new castle and town, Dolforwyn in Powys, which the king forbade. Edward declared the prince a rebel and invaded his territories with a powerful army, and by the winter of 1282, after several years of shifting fortunes, the Welsh resistance was cracked. In the north the armies of Gwynedd were dispersed; in mid-Wales the Welsh were shatteringly defeated in a battle near Builth, Llanfair-ym-Muallt, in Powtys. On 11 Dec Llywelyn himself, traveling away from that battlefield with a small group of followers, was ambushed and mortally wounded.

Weis" "Ancestral Roots. . ." (27:27), (29A:27), (132C:29), (176:7), (184A:9), (236:7), (252:30), (254:28), (260:31). According to the rules of primogeniture, Llywelyn was the true heir of his grandfater, OWAIN. In 1194, at 22 years of age, he defeated his uncle, Dafydd near the estuary of the Conwy. He took possession of the Perfeddwlad. When his cousin, Gruffudd, died in 1200, Llywelyn became ruler of all Gwynedd. About this time, King JOHN of England, was having problems with Gwenwynwyn, the ruler of the Powys Wenwynwyn, who was then the most powerful ruler among the Welsh. JOHN thought it good policy to seek the friendship of Llywelyn. Llywelyn swore an oath of allegiance to JOHN and married JOHN's illigitimate daughter, JOAN in1205.
In 1208 Llywelyn took advantage of complicated personal conflicts between King JOHN, Gwenwynwyn, and WILLIAM DE BRAOSE to take possession of Powys Wenwynwyn. About this same time, he siezed northern Ceredigion from Gwenwynwyn's ally, Maelgwyn. Llywellyn was careful not to antagonize King JOHN. He accompanied his father-in-law on his invasion of Scotland in 1209. By 1211 King JOHN, nonetheless, considered Llywellyn to be one of his most dangerous enemies and invaded Gwynedd and compelled Llywellyn to restrict his authority to Gwynedd Uwch Conwy and to recognize King JOHN as his heir should JOAN fail to bear him a male heir.
At first the other Welsh lords preferred to submit to JOHN rather than to Llywelyn. When, however, it became apparent that JOHN would not be content to rule Wales from a distance, but would be personally involved, they gave their support to Llywelyn. In 1212 Llwyleyn led the Welsh in revolt. He attacked the marcher lordships. It appears that Llywelyn had managed some sort of alliance with JOHN's archenemy, King PHILIP AUGUSTUS of France. Because of the Welsh revolt, JOHN had to postpone his planned attack upon PHILIP in France. Because of the discontent of his barons, JOHN was unable to raise an army to resist Llywelyn's advances. In fact, the barons and Llywelyn were united in their call for JOHN to submit to the provisions of the famous Magna Carta in 1215. Llywelyn's seizure of Shrewsbury in May of 1215 was a major factor in persuading JOHN to submit to the great charter.
Between 1215 and 1218 Llwyelyn and his allies captured several important marcher strongholds. Llwyelyn aimed at a status superior to that of a mere war leader and he used the structures of feudalism to strengthen his authority. He consolidated his power over the other Welsh lords by several moves in 1216.
When King JOHN died in 1216, the coalition that had resisted him collapsed. In 1218 the advisors of the eleven year old King HENRY III entered into the treaty of Worcester with Llwyelyn. Llwyelyn's pre-eminence in Wales was recognized, but he was not allowed to retain the homage of the lords of Deheubarth and Powys. The years following the treaty were marked by a strong attempts by the crown to limit Llwyelyn's influence to Gwynedd. In 1228 and 1231 Llwyelyn struck back with significant military victories. HENRY III had to enlist the assistance of Irish knights in his efforts to limit Llwyelyn's growing power as his own barons were turning against him because of his favoritism towards foreign advisors and general ineptness. Llwyelyn again, as in 1215, joined with the Norman barons against THE KING and, as a result of the peace of Middle in 1234, he succeeded in winning the same status he had during the reign of King JOHN.
Perhaps in order to stress that he was not ruler merely of Gwynedd, Llwyelyn adopted the title of Prince of Aberffraw and Lord of Snowdonia, a style which emphasized his unique position among the rulers of Wales. Llwyelyn's eldest son Gruffudd, was born to his first wife, Tangwystl, before his marriage to JOAN. Llwyelyn and King HENRY III cooperated in disinheriting Gruffudd and insuring that Dafydd - Llwyelyn's son by JOAN (and HENRY's nephew) - would be the heir to Gwynedd. This was accomplished in 1222. At this same time, the Pope freed JOAN from the stigma of illegitimacy.
There was a very close relationship between Llwyelyn's family and that of the Braose family - one of the marcher lordships. Llwyelyn's son and heir, Dafydd, married Isabella, the daughter of WILLIAM DE BRAOSE. Another of Llywelyn's children, MARGARET, married WILLIAM's father's nephew, John de Braose. WILLIAM's father, REGINALD DE BRAOSE married Llwyelyn's daughter, GWLADYS DDU. In 1030 Llwyelyn had WILLIAM hanged for, as John Davies puts it in his "A History of Wales", "excessive familiarity" with his wife JOAN. GWLADYS DDU married RALPH DE MORTIMER after the death of her first husband. With the lone exception of Gruffudd, all of Llwyelyn's children married into the families of the marcher lords.

Llywelyn Fawr "the Great" ap Iowerth, Prince of Wales who defeated his uncle Dafydd in 1194 and was acknowledged as overlord by other Welsh princes. At first Llywelyn was on good terms with King John of England and he married King John's daughter Joan in 1206. However, after King John attacked him in 1210, Llywelyn allied himself with the barons who opposed King John. When the barons pressured King John to sign the Magna Carta in 1215, the rights of Llywelyn and the Welsh were recognised.