Sibling rivalry is something that I believe anyone with a brother or sister has to deal with. I don't know of one set of siblings that at one point or another have never gotten into some type of quarrel with each other. I have one brother and we are usually off and on when it comes to fighting and getting along; some days we just can't stand each other and other days we get along like best of friends.
Cinderella and her sisters are a prime example of sibling rivalry. The older sisters are always picking on the younger one. Their situation however can not be confused with modern day children and sibling rivalry. Usually it is a little more two sided than just two kids picking on another without any kind of retaliation. .
Saying that parents influence or are the real source of sibling rivalry can be true, but the majority of the time I do not believe that is the case. People tend to get sick of each other at times when they get to know each other to well. Personal lives tend to be invaded and that usually causes tempers to be flared.
From what I've seen, siblings usually end up being almost the best of friends. Like when one moves out of the house and the siblings don't see each other as often as they used to it tends to bring the closer together and realize what they had been taking for granted all these years. .
When siblings are together, especially at an early age, I've noticed that they usually never openly admit that they love each other. That changes in time, when they realize that their brothers and sisters are really the best friends they will ever have, in most cases that I've noticed. When it comes to parents monitoring sibling rivalry, I think it should be taken seriously, but not to seriously. The kids will grow out of it.