What is with this guy?

He seems pretty comfortabl around yuo which is normal because he is one of your best guy friends, it looks like he wants to start pursuing things furhter with you, it also looks like he likes katie as well but he sees more of a fling with her but sees a relationship with you. in the long run you two will be in the relationship, just stay cool abouth the whole thing and it will all work in ur favor in the end