The Royal House of Dinefwr was a cadet branch of the Royal House of Gwynedd, founded by King Cadell ap Rhodri, son of Rhodri the Great. Their ancestor, Cunedda Wledig, born in late Roman Britain, was a Sub-Roman warlord who founded the Kingdom of Gwynedd during the 5th century, following the Anglo-Saxon settlement of Britain. As Celtic Britons, the House of Dinefwr was ruling before the Norman conquest, having to fight with their neighbors such as the Celtics, Anglo-Saxons and Vikings, before struggling with the Normans afterwards. Many members of this family were influential in Welsh history, such as Hywel Dda, who codified Welsh law under his rule, and achieved the important title of King of the Britons, or Lord Rhys, Prince of Wales, who rebelled against Richard the Lionheart, and became one of the most powerful Welsh leaders of the Middle Ages.

The House of Aberffraw was a medieval royal court based in the village it was named after, Aberffraw, Anglesey within the borders of the then Kingdom of Gwynedd. The dynasty was founded in the 9th century by a King in Wales whose descendants founded the Welsh Royal Houses. The other medieval Welsh dynasties were the Royal Houses of Dinefwr, Mathrafal.