I need help with my Siblings. Please Help?

I'm the youngest in my family and I have a brother who is about to graduate from college in May, and a sister who is a sopre in college. Since I'm the youngest, I always get accused of being spoiled and always getting what I want, even if I don't even ASK for it, my parents just give it to me, which is really annoying. Anyways, my brother and sister are within a few years of age to each other and they always chat with each other and go out to the town together, completely disregarding me. It's like they don't even want me around. I mean, I'm not a complete dork, and I don't think I embarr anyone. I'm a stinking middle-schooler, not some snotty kinder gardener. They could take me with them if they wanted to, and when I ask them if I can come, they just yell at me. My brother and sister are cool and all, but they don't seem like they want to do ANYTHING with me, almost like they hate me. I just wish I was born in my brother and sisters' time, they got to do a bunch of fun stuff together like go to Disney World a lot. Now, my parents are kind of old and we don't really do anything fun anymore like they used to. All I do is just hang out with friends. Any suggestions on how I can improve my life and make my brother and sister WANT to take me out with them? I miss the good old days when they were home. All this could be because they are older than me and close in age, but if that is the case, how can I cope with that and maybe make them want to hang out with me?