All my siblings are being annoying?

I am almost 16 and my sisters are 14 and 5, while my brother is 3. They are all really annoying and I think they all just trying to get me in trouble all the time! My 14 sister thinks whatever I own, is hers as well. I have a ripstick that I let her ride occasionally, and when I was getting ready to go to the park yesterday, she grabbed my ripstick out (without asking), so I told her I was gonna get it out (I wasn't lying, I really was going to get it) and ride it. So I asked her to hand it to me. She refused to give it to me and told me I was lying and I only wanted it because she had it. I told her its still mine anyway, and she can't get it out without asking me first. After she had a whinge to mum, she had to give it to me, but then rudely told me once I got to the end of the path, it was her turn. I said I'll decide when its her turn because I owned it, and said if she kept talking to me like that, she wouldn't get a turn at all. So I started riding it, and when I got to the end of the path, she said it was her turn, and when I said no, she pushed me off. So I got up and pushed her, then went back on the ripstick and rode off. Mum ended up getting mad at me and told me should of let her have a go, so I told her if someone was rude to her, she wouldn't let someone use her things. I got into so much trouble for being 'irresponsible'. Then my 5 year old sister will never leave me alone and will always bug me when I have a friend over. She is constantly cheeky, and when I'm nice and polite to her and ask her to get out of my room, she won't listen. So when I start to get mad, my parents yell at me and tell me that my sister isn't doing anything wrong, so she can stay in room. All I wanted was my own time, as I just got home from school and wanted to relax for 10 minutes. But obviously in my house, thats not acceptable. Then my brother is just plain annoying. If he does something wrong, my parents laugh it off, and act like its no big deal, when the thing he's doing needs to be stopped. Like my younger sister, he is constantly in my room and bugging me, and my parents won't help me get him out. Then when I do get him out, I sit against my door so he can't get back in, so then my parents yell at me for not letting him come in. What am I supposed to do? I have 3 very annoying siblings that I can never get away from.