Research Notes:

While the surviving sources are consistent regarding the parentage of Ethyll, they are contradictory regarding the identity of her husband. The mid-10th century Harleian Manuscript genealogy names the ancestors of Rhodri "Mawr/the Great": "…Rotri map Mermin map Etthil merch Cinnan…". The name of her husband, recorded in the 13th century History of Gruffydd ap Cynan which names "Rodri Mawr son of Mervyn Vrych son of Gwryat…", is consistent with this version. [The Gwentian Chronicle provides a different version of events when it records that "[the] daughter [of Cynan Tindaethwy king of all Wales] who was his heir married a chieftain of the name of Mervyn the Freckled", a later passage adding that "Mervyn the Freckled and Essyllt his wife began to reign over Gwynedd and Powys" in 818.].... ¹

Refer to notes under Nest, wife of Merfyn "Frych" ap Gwriad.