The Issue of Siblings

It just suddenly daunt onto me that I seen to have something against my younger sister no matter what she does. Serious. Every single thing, most of the time, I cannot stand her. Sometimes and very rarely, we seems to hit it off okay, but most of the time we bit the heads off each other. Legend has it that to be siblings, 2 person would have cultivated some kind of 'karma' or whatever it is called in your past few lifes. I guess it is not all that true ya. If it takes so many lifetimes to cultivate this sibling-ship, why is it that we are fighting every single day for almost everything? Such a waste of time. Fight, fight, fight. That's why I kind of envy those people with fantastic relationships with their siblings. They treat each other as best friends and tell each other everything, do everything together... Seems kind of nice doesn't it? My sister thinks that I have some mental problem to be against her all the time. I think that my sister have a lot of growing up to do and she is worst than a 10 year old kid. What seems to be the problem?