where do i belong

So I have a crazy family, my mom has 6 kids other then me, and my dad has 2 other kids. All my moms kids have different dads, every single one, and my youngest sisters dad spoils here rotten, while me and my other sisters are stuck strewn across the country. My older sisters were in foster care until they turned 18 and me and my younger sister got adopted by grandparents, she's with moms family and I'm with my dads family, so for all of us to have a relationship is kind of hard. Luckily for my youngest sister she is spoiled rotten, and she gets whatever she wants, so when she asked for season passes to six flags her dad of course said yes, and so he go one for me and my two younger sisters and said he would pick me and my sister up every time they went, which was soooo exciting I was so happy I was gonna be able to spend time with my sisters, have an actual relationship with them. He picked me up twice and that was it. I haven't seen either of my sisters since, not because he doesn't still take them, but because he just doesn't want to take me.. He still picks up my other sister he just doesn't come get me or even see if I could get a ride to his place and go with them. I never know until after they go, when my sisters post facebook pictures of them at sixflags, and it makes me feel like I don't belong. I don't belong with my sisters and now I don't belong with my dad either. I say that I don't belong with my dad either, because him and his girlfriend went on a family vacation, and I wasn't invited or given any money to feed myself or their dogs that I got stuck babysitting. It made me feel like I wasn't part of their family, and then my dad always tell me that no matter what happens even if his girlfriend is wrong he'll take her side, which makes me feel like crap. I don't know what to do, until I have money I can't afford an apartment, but I hate living here, I feel like I don't belong anywhere right now...