Book of Genesis Theme of Sibling Rivalry

Remember the first time you called your brother a weenie? Well, Genesis will make you feel like that was the nicest thing in the world. See, the siblings in Genesis skip straight to murder, crime, deception, and revenge. But here's the thing. All this stuff is pretty nasty, sure. But it's also God's will. How do we reconcile this?

Oh, and can we invoke God's will next time we give our little sister a wedgie?

1. Are there any brothers and sisters in Genesis who don't want to kill each other? Why are the issues so often between siblings? Why not between parents and children?
2. Which siblings prosper? How do they gain an edge? 
3. Are parents ever guilty of egging on these rivalries? 
4. To what degree are these rivalries provoked by God?