Question: Rhiwallon ap Cynfyn, was a Welsh King, following the 1063 invasion of Wales by Harold and Tostig Godwinson, he was an Anglo-Saxon Earl of which location, that overthrew Gruffydd, Rhiwallon and Bleddyn jointly?
Sentence (from "Rhiwallon ap Cynfyn"): the son of Cynfyn ap Gwerstan and brother of King Bleddyn of Powys.
Relevant evidence: No