Bartum argued the two names Custennin Gorneu and Custennin Fendigaid, that of the brother of Aldwr, refer to the same individual citing ByS 76 as one piece of evidence:
“Thus Custennin Gorneu and Custennin, the grandfather of Arthur, have been tacitly identified. Further confirmation of this is the fact that Erbin ap Custennin is said to have been uncle to Arthur, and Geraint ab Erbin first cousin to Arthur in the tale of ‘Geraint and Enid’ …”
However, that passage has been influenced by Historia Regum Britanniae which attempts to claim a Breton ancestry for Arthur. The following table shows that Custennin Gorneu was of gen. -2 whereas Custennin Fendigaid, being the brother of Aldwr, was one generation earlier:
|Gen.||ByS 26||CB||ByS G 24a|
|0||Selyf||Gereint||Hoelus Secundus||Howel vychan|
|-2||Custennyn Gorneu||Budicus||Emyr Llydaw|
The names in the above table are as they appear in the document. Note, ByS 26 has been adjusted to show Cybi as being the son of Selyf ab Erbin as indicated by his Vitae. As indicated by ByS G 24, Budic was referred to as Emyr Llydaw. This can be confirmed by looking at parallel entries in the HRB and the ByB.