Relius - I think Gen was testing him when he asked if he hated Attolia now. If the answer had been yes, maybe Gen would have left him to his fate. But once he was sure that Relius was completely loyal he was able to save him, for Attolia's sake as well as Relius's. Oh, and as sgwordy said, Gen wanted Relius to understand Gen's love and loyalty towards Irene regardless of what she'd done to him in the past.

I also think Gen felt a tremendous amount of sympathy for Relius, who was afraid, and in pain, and in danger of dying in Attolia's dungeon. Gen knew what that felt like. He's very caring in his repeated visits to the infirmary, and the kiss, though meant as a joke, was the result of a combination of many things.