My step brother kissed me and now has a girlfriend!

Last your in August I met my dad's girlfriends son who is 14 and I am 16. From the beginning we became really close. He goes to boarding school by tries to come home every weekend that he can. While as school he would text me every week or so just for a chat and when at home he would always try to touch me in some way either by hugging me, hitting me with pillows or sitting on me. He is always joking and making me laugh and I always catch him looking at me sometimes he hold eye contact and other times he looks away quickly. He also sings songs to me like total eclipse of the heart and always by blink 182 to name but a few. When talking to him we have strong eye contact most of there time. In February this year one night he came over beside me, kissed me on the cheek then the lips then proper kissing and so on, there was touching but we didn't go any further than that. He then went to be asking me if this was only a "one time thing" and I said yes it was. He came back down stairs an hour later and we did it another 3 times. Two days after I text him asking if we were going to talk about it and he said we shouldn't because it was a "one time thing". The next time I saw him he was very distant and he stayed away from me for the whole weekend, like I had the plague or something. The next time however he kissed me again like that twice. Two days later I find out he has a girlfriend and has had for about a week so he cheated on her with me, on the week of her birthday party she is having at her house where he is going to meet her parents. Over the course of knowing him I have fallen for him, wrong as it is and I have tried to forget about it and move on. And now he is bringing the same girl home for the weekend to me his mum, my dad and I and it makes me quite sad really. He never mentions his girlfriend to me apart from to make me jealous by saying things like "I'm away for a two hour phone call" which is impossible as we like in the country and have no signal on any of our phones but he pretend to talk to someone for about 5 minutes and it couldn't have been the house phone as they were both downstairs and it was skype or anything because we had no internet connection at that time. He hardly text me anymore but our relationship hasn't change apart from that. And I just would like someone to tell me what is he doing? And where do I stand with him and is there any possibility that he likes me back? I have no idea what to think and its killing me because I hate this. I hope someone can help me. Thank you and sorry for the length of the story x