Janny - are Royal lines and their Caithdienen geas matched to keep a kind of balance?
If S'Gannley has the seer's vision of truth, I can see how that would balance s'Illessid Justice - for Justice needs truth in order to be fair.
S'Falenn compassion is partnered by S'Valerient vision...?
Roisin - You Asked.
There is more on this in the appendix (US edition) of Traitor's Knot.
The Fellowship Sorcerers chose the lineages, so yes, clan gifted talent would have come into consideration.
Of far more weight was individual character: the ability to discern and perceive, and if need be, challenge the one crowned. Backbone was the essential characteristic.
Since clan lineage and gift would have contributed to discernment, and the necessary clarity to preceive, the answer to your question is yes.
Geas comes up often in celtic stories as a kind of birth born taboo - that certain heros and kings were given geas that prohibited them from doing certain things, and that if they broke them all, they would die! One story of Cuchulainn, the Irish warrior, said that two of his nine geas, were that he could not eat dog (his totem) nor could he refuse an invitation to food - so of course, one day he was invited to eat dog... ouch.. what do you do then?
It seemed that these geas were given to people of responsibility - who preserved the sanctity of the land, the kings, queens and warriors. Poets and druids, who were the keepers of the law, were not born with geasa.
Interesting to read the WoLaS take on it.
I had a hero in my mind and he had a geas placed on him. I have to study about geas more before I do anything more on that idea. Patricia Bray has a great hero with a big geas on him. He's Devlin and it's a great trilogy. I need to recommend her in the book nook area. I love geases in fantasy though. Thanks for that info. on geases Roisin. It was interesting.