Merfyn ap Rhodri
Merfyn ap Rhodri (died) was a late 9th-century Aberffraw prince of Gwynedd.
He is sometimes credited with ruling Powys after the death of his father Rhodri the Great in AD 878.
In the accounts where he is credited as a king, he is reported to have lost his realm to an invasion by his brother Cadell, King of Ceredigion.
Merfyn's death may be connected to the incursion into Anglesey by the Viking Ingimundr in the first decade of the 10th century.
The drowning of his son Haearnddur, or "Haardur", was reported by both the "Chronicle of the Princes" and the "Annals of Wales".
The first places it in the year 953; Phillimore's reconstruction of the latter's dating would place it in 956.
Kaya Alp
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Lyon Cohen
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He was the grandfather of singer/ poet Leonard Cohen.
John Westley
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Henry Krause
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He played college football at St. Louis University.
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Ethyllt ferch Cynan
Ethyllt ferch Cynan, also known as Ethil, was the daughter of King Cynan Dindaethwy ap Rhodri of Gwynedd.
Fred Le Deux
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Llywelyn ap Merfyn
Llywelyn ap Merfyn( died 942) was an early 10th- century King of Powys, son of Merfyn ap Rhodri, and grandson of Rhodri the Great.
Rhodri the Great
Rhodri ap Merfyn (820–878), later known as Rhodri the Great , succeeded his father, Merfyn Frych, as King of Gwynedd in 844.
Rhodri annexed Powys c. 856 and Seisyllwg c. 871.
He is called "King of the Britons" by the "Annals of Ulster.
" In some later histories, he is referred to as "King of Wales", although the title is anachronistic and his realm did not include southern Wales.

Question: Who is Merfyn Ap Rhodri's paternal grandfather?
Answer: Merfyn Frych