It is known that Roderc (or Riderc) was a contemporary of Columba, but the date of his death, dependent on the 12th-century Life of Kentigern and an entry in the Annales Cambriae an.CLX+9 Conthigirni obitus...., is unreliable.
Furthermore, it is not clear what the sources for these genealogies were, and to what extent they are independent and factual, or how much they relied on much the same evidence we have today; and, if they lacked information, whether they supplied it.
The most famous figure in the list after Roderc is Eugein map Beli, who is no doubt intended to be Ohan (AT) or Hoan (AU) a king of the Britons who slew Domnall Brecc in an ambush in Strathcarron in 642.
This battle is the subject of an awdl in the Y Gododdin collection, but in the poem the victor is not named, only said to be a grandson of Neithon (according to an emended reading of the surviving versions of the text).
There is no reason to associate Ohan with Alclut, but the genealogist probably felt there was no harm in inserting such a prestigious character, and his grandfather, into the genealogy, particularly if there was a substantial gap to fill between Roderc and Guret, and he may possibly have been the father of Domnall (although the name Ohan/Hoan/Auin/Eugein is very common).
It may well be that Ohan's action led to a decline in the power of the Cenél nGabráin and subsequent reoccupation of Dunbartonshire by the British under Gureit.
It is likely that, if there is any truth in the poem, Brude's father was Bili mac Elphine who died in 722, and that his son predeceased him in 693.