It's a secret.
5 days: Leaf and Nanna from
FE5: Thracia 776.
Well they were in FE4 first, but FE5 is their game.
Cuan and Ethlin's son and Lachesis and Fin's daughter =] That's pretty awesome.
I actually paired Lachesis with Lex when I played the game because Fin doesn't have holy blood >_< But really, I'm a fan of the pairings portrayed in the Oosawa Mitsuki manga.