Help me

So I have these two really good friends named Mary and Rachel and Mary dated Rachel's brother last year but I like Rachel's brother and she knows and she is mad and isn't even talking to me... I don't know what to do cause her brother likes me to and he is already talking about kissing me (I've never kissed anyone before) so I'm kinda nervous (I'm 14 almost 15 and he's 15 almost 16)