This line is correct as to relationships — see the links in the profiles — but the dates are, actually, unknown.
Except in extremely rare instances we do not have birth dates for any medieval people. Really rare. Even royalty.
So the birth dates are always guesses, sometimes intelligent guesses with a lot of thinking about history, sometimes just guesses.
We do have seat dates, for important people. At least sometimes.
But of course not always.
So what happens is that different genealogists or amateurs or historians make different guesses, which show up in different sources, and then get copied into data bases (like the one), and because the dates often come from different sources, they often don’t make sense together.
Presumably the all looked like they made sense, separately, in their different realms.
So I can go clean it up — we have most often been using Darrell Wolcott’s dating system, as he’s working with the genealogies and the chronicles and the land documents and history, to make the Welsh tree make sense.
Steven Mitchell Ferry — what’s going on is that Wolcott has figured dates for Maredudd, and dates for Arthfael Hen, but the connection between them, Ceingar, has no Wolcott citation; the connection is given by Bartrum.
And the Wolcott studies for the two men are different ones.
Does Wolcott address Ceingar at any point?
Wolcott has not addressed her in his publications. As a daughter of Maredudd ap Tewdos she should be dated at c. 775/780. Arthfael ap Rhys is at c. 665, so she cannot be his mother. Bartrum himself, in his Glywysing and Gwent chart (https://cadair.aber.ac.uk/dspace/bitstream/handle/2160/6516/TABLES%...) shows a great deal of confusion and corrections as to whom he thinks she might be. I would suggest that he has conflated two or more women with the same, or similar names.