It is not therefore known whether Gruffydd and Elisse were sons of Cynan King of Anglesey/Gwynedd or grandsons of Cadel King of Powys.
The chronology appears to favour the former interpretation, but the uncertainty of the chronology of all these early sources is recognised.] .
Another view concerning the difficulty of accurately reconstructing Welsh royal genealogies is given by Bridgeman in the introduction to his History of the Princes of South Wales.
He states that The chief difficulty which meets the student of Welsh medieval history is the scarcity of official deeds.
It appears to have been first published in the late 18th century by Edward Williams (also known as "Iolo Morganwg") who was "considered an authority on Welsh literature and folklore at the time, but was revealed as a forger in the twentieth century".
The extent of the fabrication of the Gwentian Chronicle is not known: clearly it includes some reliable information as many of the statements coincide with what appears in the Annales Cambri and the Chronicle of the Princes. After analysing the possible origin of the so-called Gwentian Chronicle in several other earlier manuscripts, and discussing the problems in detail, Stephens concludes that "that it abounds in mistakes, conjectures and unauthorised additionsseveral anachronisms" but that "it has many parallelisms with Brut Ieuan Brechva", suggesting that "both the Book of Aberpergwm and the so-called Book of Caradocaredocuments of the sixteenth century".
[The Gwentian Chronicle records that "Cadwallawn son of Cadvan king of the Britons" died in 660 (dating seriously awry) and was succeeded by "his son Cadwalader the Blessed".] After his father's death, the throne of Gwynedd was usurped by Cadafael ap Cynfedw, who was deposed in 654 by Cadwaladr who then succeeded as King of Gwynedd.
The Annales Cambri record the death of "Catgualart filius Catguolaum" in 682, killed in battle (-[Rome 20 May 689]).
Bede records that "rex Brettonum Ceadualla" killed "Osricum" [King of Deira] in , and ruled "provinci Nordanhymbrorum" for a year before also killing "Eanfridum" [King of Bernicia] who had visited Cadwallon to sue for peace.
The main Welsh primary sources so far consulted in the preparation of the present document are the Annales Cambri, the Chronicle of the Princes/Brut y Tywysogion, and the so-called "Gwentian Chronicle".
Numerous extracts from these works have been incorporated, although it has proved difficult to identify all Welsh persons who are named, particularly for the later years.
Indeed, it is possible that Ethyll was not a historical figure at all but was invented to legitimise the dynastic change in the eyes of successor generations of kings and their supporters.] [either: ETHYLL of Gwynedd, daughter and heiress of CYNAN [King of Gwynedd] & his wife ---, or: NEST of Powys, daughter of CADELL ap Brochwell King of Powys & his wife ---.
[The Gwentian Chronicle records that the mother of "Mervyn the Freckled" was "Nest daughter of Cadell of Derrnllwg, son of Brochwel Ysgithrog", after recording that "[the] daughter [of Cynan Tindaethwy king of all Wales] who was his heir married a chieftain of the name of Mervyn the Freckled".