There is one other thing to consider, though, while talking about life with a sibling. I choose to call it the 'best friend clause,' particularly for siblings close in age and living together. It's as if, when deciding to have multiple children, your parents signed some imaginary contract agreeing that they hereby accept the risks of forcing you to spend your life with this other human being, seeing as whether you like them or not, you are stuck with them. But there is a bright side, or at least I'd like to think so. Somewhere along those years of crying, antagonizing, hating, beating, stealing, yelling, throwing random objects, and performing highly dangerous, high risk wrestling moves on each other, you may come to find that even when you are mad at them or they are mad at you, your siblings can be your best friends. I'm sure most siblings experience this at a very young age - probably only because you're young and don't really have any other friends, anyone else to play with - and then you grow up, look at your siblings and think, wow, what dorks. A select few of us, though - and I consider myself lucky to be in this category - are surprised to find later on in our teen years really how much we appreciate having a sibling. For years I couldn't wait for my sister to go to college and get out of my face, yet now that she's gone and I've taken to having almost nightly conversations with her, I roll my eyes at the unfortunate realization that I actually do kinda miss her.
You never know when, at those unexpected moments, a sibling is going to outshine all expectations; lend a hug when you need one, be a friend when you feel like you have none, sit up at watch tv marathons with you into the late hours of the morning, or help you think of mean, behind-the-back insults toward someone you feel like being particularly mad at at the moment. Its like siblings are..."rent-a-friend"s. There will always be disagreements, fights, arguments, and such, yet it's surprising how often a sibling will readily be there for you when you need them. Surprising for me, at least.
So, in those dark times when you really, really feel like punching a sibling in the face, just bear in mind - deep breaths, calm thoughts, and no headlocks. Its what siblings do; you cant blame them for being what they are :)