Bartrum argued that Maeswig and Mar were names for the same individual. However, to understand why this was not the case we need to begin with Onnengreg f. Gwallog m. Leenog who ByS 48 tells us was the wife of Meurig ab Idno:
|Gen.||ByS 48||ByA 13||ByS 12|
|0||Leenog||Meirchion||Pabo Post Prydyn||Lleenog|
ByA 13 provides additional information that Meurig had a brother named Mabon and that Idno was the son of Meirchion. We may, therefore, conclude Meirchion and Leenog were of the same generation. The question is which generation. Bartrum adopts the view that the father of Idno was Meirchion Gul, an assertion that appears in the ByS G 54 of c. 1510, see diagram below.
However, this descent, which implies Idno’s father belonged to gen. -1, is not shown in any other source. ByS 12, see the table above, shows Lleenog belonged to the same generation as Pabo Post Prydyn who is known to have belonged to gen. 0, see Pabo and Sawyl, allowing us to conclude Meirchion and Leenog were also of that generation. We may now maintain that Maeswig Gloff, the father of Leenog, was the son of Mar ap Ceneu as shown in the table below.
|Gen.||HG 9||JC 36||ByA 28c|
|-1||Maeswig Gloff||[Maeswig Gloff]||Einion|
|-4||Coel Hen||Coel Hen||Coel Hen|
ByA 28c demonstrates that Mar belonged to gen. -2 and so we can discount the possibility tha Maeswig was the father of Mar. Curiously, Bartrum’s assertion, whether right or wrong, that Ceredig ap Gwallog died in 620 is more in line with my analysis rather than his own.