Sibling Rivalry

In Genesis 4, the issue of sibling rivalry arises. While Cain presents God with the sacrifice of fruits of the soil, Abel presents God with fat portions from some of the firstborn of his flock. It appears obvious that God favored Abel's offering over Cain's. Of course, as any sibling would feel angry and inadequate at this point, Cain feels resentful. He then kills Abel and when God asks where Abel is, Cain eventually admits to killing his brother. While this acts as an extreme example of a clash between sibling, that rivalry does exist. 

I don't have any siblings; I don't know all there is to know about why siblings act the way they do towards each other. So I can't really say much as to why this constant bickering and hostility exists. However, I do know that when competing for the love of parents, it's a stressful situation. In Genesis, it's obvious that both siblings want to be loved by God, and when it appears that God prefers Abel to Cain, of course feelings will be hurt. We have to remember we are loved, nonetheless, and to stop competing with those we love.

 https://www.google.com/siblings