Why do my parents treat my little brother better?

Don't think I am being stupid or mad or anything! I really need help! Okay, I always try telling my mom how i feel but she always tells me to grow up or stop being a baby. I am 13 years old and my little brother is 8. My mother thinks that his excuse for being a total female dog is that he is younger and doesn't know better. I cry continuously because I feel I am being treated like crap. He physically and emotionally abuses me and I can't handle it anymore! All I want is to have an understanding family and kind little brother. I am trying my best to be nice to him. He will call my mom at work and out of the blue tell her crap like "Kaitlyn slammed my finger in the door" or "Kaitlyn scratched my leg" even after I do nice things like help him on the computer, make him brownies and lemonade, cook him lunch, clean his room, get him dressed, do his hair, sew his ripped hat, etc. Then he backstabbes me for no clear reason! Should I trust him any more? This onrey attitude started like a year ago. It is breaking me down. I feel lost and trapped. I feel like I am not appreciated enough. My little brother got a terrible report card and my mom shouted for joy and bought him an pirate lego thing that costed almost $100. I had gotten one B and all As and all she could say was "Yea great job. You just need to move that B up and then we will see." Now thanks to him, I cannot babysit him over the summer to make some well needed money because he caused an incodent i mentioned earlier. Please help me. I would really appreciate it if you gave me some advice and told me what is going on here.Thank you! (P.S. Please leave no rude or unrestricted comments just because you think it will be funny of you to hurt my feelings!) And please be gentle! I bruse like a peach!!!