Llywarch ap Hyfaidd (?-904) was the king of Dyfed until its conquest in 904/905 by Cadell ap Rhodri and his son, Hywel Dda. Kingship passed briefly to his brother, Rhodri, until rule was consolidated by Hywel. Hywel married Llywarch's daughter, Elen, to legitimise his claim to the throne. (Wikipedia)