Planning on making Genealogy-based teams between two different accounts.

First account has Sigurd and Deidre and thinking between Eldigan, Lachesis, Arvis. Is there a final complementary unit for them especially for Gen1 Genealogy? I assume Finn is the only blue Genealogy Gen1 available right now. If this is the case, who seems to be the best combination out of these all?

Question is the same for the second account except it uses Gen2. Base team is Seliph, Julia, Ishtar. Looking for a third and thinking between Nanna, Julius, or Saias. Finn may also be accepted as well as Rein or Olwen? The last two seems like a stretch. Anyway, betwen these choices, who seems to be the best fit to complement each other especially in lore standing.

Currently not yet planning on their SI and other builds since this is mostly done for fun. I will, actually, very likely try to maximize their potentials over time though.