I wonder how much difference there is between 'spurious pedigrees' and 'fictional genealogies' when we go as far back as these eras?
To me the Orkney Jarl's sagas are less about establishing pedigrees (although they are that too) than about creating a narrative continuity (according to Terry Pratchett, "Humans add narrativium to their world. They insist in interpreting the universe as if it's telling a story. This leads them to focus on facts that fit the story, while ignoring those that don't")
So the Karl Hunderson of the Orkneysagas may or may not be the Viking name for Macbeth, and may or may not be the Henderson family progenitor – but this is not a question of spurious genealogy, so much as poetic licence and linguistic differences lost in translation.
And Eithne / Audna Kjarvalsdatter, Princess of Ireland Audna, fabled to be Cearbhal’s daughter, is obviously spurious, as she’s born 30 yrs after his death –(so I’ve finally had to lock her profile to stop it being reconnected to him); but it is an important part of the story of the gentic link of the Orkneyjarls to Ireland, and the narrative connection suggests to me there’s a good chance she is a gggranddaughter – though no way to prove it.
Shakespeare’s attribution of Banquo to James I’s pedigree is more clearly spurious genealogy, for me.
