The Royal House of Dinefwr was a cadet branch of the Royal House of Gwynedd, founded by King Cadell ap Rhodri (reign 872–909), son of Rhodri the Great.[1][2] 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 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.[3][4]