Why was this guy ogling me while he was making out with his girlfriend?

I was out with a few friends and two of them are in a relationship. Basically he started making out with his girlfriend (french kissing) who was sitting next (we shared a lift home from a friend) to me but his eyes were open and he was staring at me the whole time her eyes were obviously closed. Don't you close your eyes while kissing someone especially your partner? I was kind of uncomfortable. And he also had his arm around her (she was sitting beside me in the nightclub) but his kept tipping me on the shoulder behind her back i just ignored him. I think he fancies me a bit ive only met him a few times but he always comes over to talk to me. It was my birthday and he kissed me on the cheek and he kept asking some other lad (who is also my friend) to kiss me. He also got into bad humour with his girlfriend and he just walked off and sat somewhere else in the nightclub. I don't think it was over me but they made up later that night.