I think it depends really. With Lee and Casey, I think they're both just horny and like each other but on Lee's side I'd say that their is some possibility that he's playing up to the cameras now he thinks he's up for eviction. I say that purely because he said before he went in that he wouldn't kiss anybody in the house because of his kids. And I'd say that kids come before 'horniness', so I think there's more to it than him just being a bit horny.
But so far people that know Lee are just saying that he just falls for people easily, so it might just be mere selfishness and immaturity.
And it's not just about them staying in the house longer because they want to get as far as they can. Lots of celebrities go in for profile and a showmance would be sure to get people talking. Is Lee perhaps in need of profile?