What are you supposed to do when you have a very condescending, rude and nonsupportive family? I NEED advice?

Ok first of all family gatherings have become intolerable. I can't stand going to them anymore. I'm 16 so I really don't have the choice to avoid them, unless I conveniently have to work or go somewhere else that day, but that never works. My extended family (aunts, cousins, uncles, grandma etc) are very rude and never want to listen to a thing that you say. They ask you questions, but they only want to hear only like a five word answer and the questions are always about the same old things (school, what I'm doing in my free time, whatever). After you try to get a conversation going, they make it very obvious that they are not interested, not listening and they start walking away while you are answering/talking about a question they just asked! My family always gets the feeling that at family gatherings (especially the christmas parties, yuck!) they look down upon us because we are not rich like they are or we don't own horses like one of my adult cousins, and we don't do things like our other family members etc... I am sick of getting treated like this! My grandma doesn't give a crap if I have a 4.0 GPA at school, I play guitar and I'm taking college cles this year for school even though I'm only a junior in high school, but she does if my other cousins talk about that kind of stuff.I had been playing guitar like a year and a half before any of them knew! I get completely ignored and my dad, mom, sister and brother do too. We could go through an entire christmas party or whatever without even talking and no one else would notice. My aunts pawn my grandmother off on my mom even though she is busy with work and she still has three kids at home to worry about. They always make my mom deal with her because they don't want to, so my mom has to make schedule changes. My grandmother sometimes isn't the nicest person in the world and complains about everything. My parents will go out to dinner with me and maybe my sister/brother and then grandma will come along. That's fine except my parents pay for her meal and she will complain about the food the entire time and watch me eat. She still treats me like I'm three and asks me in the tone commonly used for 3 year olds if I can eat all my food like a good girl. My cousins haven't said more than two words to me in probably like at least five years even though we see eachother 1-3 times a year (they all live in a different state). I have two girl cousins and they do not talk to my sister and I because they treat us like we are less than them. I have another set of cousins that are brother and sister (they a have a flake for a father, sadly my uncle and my mother's brother) and they think that they are gods and no one is better than them. Everyone wants to know what they are doing, but not what we are doing. My sister joined the military and has been in for almost two years and when she came back from basic training for her christmas break, we had to go to a family christmas party. She told everybody about her choice and everyone looked at her like she was an alien. They pretty much in so many words thought that she was stupid for doing that and they did not care/support her whatsoever. My other aunt is very nasty and is not afraid to say what is on her mind and even told my cousin a few weeks before he was going to get married that the marriage wouldn't