Question: Why did Rhun Hir Ap Maelgwn's father die?
Sentence (from "Maelgwn Gwynedd"): The son of Cadwallon Lawhir and great grandson of Cunedda, Maelgwn was buried on "Ynys Seiriol" (now known as Puffin Island in English), off the eastern tip of Anglesey, having died of the "yellow plague"; quite probably the arrival of Justinian's Plague in Britain.
Relevant evidence: Yes