First sibling fights

Now that my brother is more interactive, we have more fun together! I pretend he is a monster and scream scrambling away from him while he crawls after me giggling. I play catch with him (or rather, I throw the ball and I pounce on the ball before he can get to it). Most of the time, he's like a pet, and I laugh at him or protect him (usually from stairs). But now that he is more mobile, he also gets on my nerves sometimes! Before he used to be so easy; all I had to do was wave another toy at him and he'd drop whatever he was doing. Nowadays, he is becoming particular in what he wants and protests if he doesn't get it! So he has been crawling up to me and grabbing things away from me, and messing up what I've been playing with. I get so annoyed!!! Sometimes he is halfway across the room staring innocently, and I am freaking out about him grabbing my things! I don't like that I have to share all of my toys which used to be all mine. I put stuff in high places, and hoard things so there is nothing left for him to play with. I've never been interested in balls, but now that they are Sebastian's favorite toy, I suddenly NEED to play with and have all of them! So my parents have been mediating our "fights", and not necessarily in my favor any more! Hey, it's not fair because they make me share, but Sebastian doesn't know how to reciprocate! I don't mind having Sebastian around, but everyone's gotta learn that this house revolves around ME!!!