Crixus indeed have fallen in love for Naevia! The proof of it was Spartacus: Vengeance Episode 4 where He and Spartacus decided to save her in the mines where only half of the gladiators decided to come! This was a risky move and that it’s too dangerous knowing that Romans soldiers are both present in the area! If you think about it, you’ll definitely say that this is a do or die rescue mission where one false move can send them all to death which what have happened to some of them.
