One of the ugliest feelings on earth is Jealousy. It is some times referred to as the "Green Eyed Monster."
No one ever profits from jealousy. In most cases jealousy just hurts the people you love the most that are around you.

So why is it so common amongst siblings? Why do friends and lovers experience such a negative emotion towards someone they care so much about?

Siblings often compete for attention. They also compete to find their place in the family. It is so hard for Parents to always be fair in every area.
I know we try hard not to make differences in how we treat our children. But one child's best may be another child's normal achievement.

So it is fair to say that in school when it comes to grades. Children have to be looked at on an individual level. You might scold one child for obtaining a "C" in English. While you may need to praise another child for that same "C" in English.
Because you know how difficult English is for the second child to accomplish a passing grade.

Explaining the law of individuality to children is a place to start if you see tension building and Jealousy peaking it's nasty head up between your children.

In most cases kids will understand what you are saying if you talk to them alone and on their own level.

It is also important to spend time with each child alone. Doing something that they like to do best.
It gives you time to communicate openly and keep a good relationship with each child.

When life gets busy it is very important to keep in contact with how everyone is doing. If anyone is feeling left out or alone.

When you try your best to keep things on an even level. Jealousy can not fit in to a close loving family. And....when and if it does...you can chase it away with kind words and good communication.