Important clues about King Arthur
The triads are especially useful in tracing genealogies, for instance: Triad (70) (fair womb-bearers) states "Owain and Morfudd (son and ) daughter of Urien, and Anarun archbishop of Llydaw, by their mother Modron daughter of Afallach;" which relates to the Island of Afallach in Triad (90) which is one of the three important saintly harmonies, which relates to Triad (51) where Arthur is taken to the Island of Afallach being mortally wounded after Camlann. Note that Afallach's other grandson is called archbishop of Llydaw (meaning Brittany - Arthur is revived and becomes St. Arthmael (Armel) in Brittany, but that is another proof) and that there is a lake in Snowdonia National Park, in North Wales called Llyn Llydaw. Local legend believes that Sir Bedivere threw the sword Excalibur into this lake. Returning to Triad (52) (Exalted prisoners) we see Mabon is son of Modron, who was stolen at birth and placed in prison. He is rescued from prison by Arthur's men Cei and Bedwyr riding on the salmon of Llyn Llyw in the story Culhwch and Olwen in the Red Book of Hergest and White Book of Rhydderch now grouped as the Mabinogion. Returning now to The Island of Afallach, it can be none other that Bardsey Island, "the island of 20,000 saints" and Modron can be none other than Morgan LeFay.
In Triad 70 Modron is shown to have twins (son: Owain and daughter: Morfudd) to Urien and thus Gwrgant the Great is the same of Urien of Gorre (Gower). In the Life of St. Pol it says that Count Withur (Gwythyr) and he are cousins. (See Lives of the British Saints: St. Pol). The Corrected Triad 56 shows: Gwenhwyvar (Guinevere), wife of Arthur, as daughter of Gwythyr the Enemy-subduer (Greidiawl), son of Owain the Great of Gwent son of Urien of Gorre (Gwrgant the Great).
Important clues about Merlyn
Another interesting genealogy is: Menw son of Teirgwaedd one of Three Enchanters of the Island of Britain in Triad (27) who also appears in Triad 29 (18) as Menwaed of Arllechwedd (Menwaed is the same as Menw son of Teirgwaedd being a concatenation of Menw and Teir-gwaedd). (Arllechwedd is a cantref of Gwynedd which includes the western Conwy Valley and thus places it near Dinas Emrys.) In this triad Menw is the father of Mael. There is a unique statement included in this triad that "Arthur composed the poem to his three battle knights, one of whom is to Mael the Tall". (In Triad 123 . Arthur is called one of the vain or frivolous bards of the Isle of Britain!) This Mael could be St. Mael who was related to St. Sulien and St. Cadfan (all three of these saints went to Bardsey Island).
Thus we have these clues about Mael:
Thus, putting these clues together: Merlyn = Menw = Elffin and that Taliesin is his apprentice. When the boy answers Vorigern's question what is his name in Nennius, he answered that he is "Ambrosius (Emrys Wledig)" meaning that he was his cousin, or maybe he is 'shape-shifting' him, thus Geoffrey's "Merlin, who was also called Ambrose"! Noting that this is a child, Merlyn would still be alive up until Camlann in 539.
There is another Merlyn called Myrddin Wyllt from the North contained in Triad 125(87) and his geneaology shows him as the son of St. Madog Morvryn who in the chart of Coel Hen is a contemporary of Pablo Post Prydain whose death is dated in Annales_Cambriae as 597, 79 years after Arthur's victory at Badon so Myrddin Wyllt would not be a contemporary of Arthur.