he has a gf, then why does he act like this?

ok so my brothers"s friend is 17 and he's so hot, he always looks me in a way that makes me blush and i knew he liked me but yesterday he stayed over and like at 1 he came a laid with me and started to cuddle with me and i asked him what he was doing in my bed so he just said is better to sleep with you than in your brothers room, so we started talking and then he stared tickling me but i could tell he was trying just to touch me, well today when i woke up of course he wasn't there anymore but he was downstairs with my brother and we decided to go swimming and i was wearing a two piece and he saw me and said damn but my brother told him to back off, when we were playing ball in the pool my brother went to get some pop to drink and his friend kissed me really hard on the lips and even pushed me against the pool wall while doing it. he didn't say nothing afterwards but why if he likes me doesn't he do something about it? i'm 14 by the way.