From what I've played, attempted to put into male/female pairs.
FE4: Ced/Ayra
FE5: Leif/Olwen
FE6: Klein/Ekhidna/Fae (SO FLUFFY AND CUUUUTE)
FE7: Hector, Karel, and Pent/Farina (FIGHT ME, FIGHT ME ALL OF YOU) and Nino... though tbh it's hard to pick a character I like more then others by a large margin besides those four I guess. I don't hate a single character in this game.
FE8: Joshua and Cormag/L'arachel
FE9: Haar/Titania, Jill, and Nephenee
FE10: Same as above...
FE13: Lon'qu and Inigo/Cherche
FE14: Leo/Oboro