TEENS: Do you think this is unfair? Or am I the only one who sees it?

I understand where you are coming from. You are only 15 so you still need to be taken care of financially. I think he is a bit out of line, especially when it is your mother you are asking. Yes, Kim is his daughter, and she is obviously going to get more than you, but it is your mom's business whether she decides to give you money or not. Talk to your mother about it in private so that he can't in. I am sure that she feels that Kim is a spoiled adult too! Which she is.