Every trouble in a child's life is the result of something. Sometimes, simple unawareness in the childish psychology could cause many uncured psychological complexes and troubles. Every children psychologist suggests that it is better to prevent than to cure.
Competition between siblings

Competitive behavior between brothers and sisters is natural, but sometimes a child starts fighting as if it is the most important battle and there is only one final result – to win. For what? Parents' attention, beautiful toy, and better attitude... whatever it could be, but these children are yours; try to do everything possible in order to understand them if the competitions turn to be rivalry. When a child starts to analyze his/her life, he/she used to define his inner "I" and compare himself/herself with the closest person (who is closer than a sibling?). The worse result of such rivalry is jealousy. For example, one of the siblings is talented in the arts; another one is less successful in that. The second child might develop jealousy as for his/her brother or sister. The signs of that is regular arguing, evil observations, desire to lower the achievements of each other, quarreling about minor things, unwillingness to discuss own successes. If you notice such behavior of a child, speak to him/her and try to point out the reasons of his/her non-adequate relationships with a brother or sister. Usually, a child needs attention and some tips. For example, tell your kid that he/she is not worse than his/her sibling is. He/she is just another person with own talents and abilities. If one of the siblings is better in the running, another one could be more brilliant in studying.
Moderate competition is logical and even needed as it is one of the everyday life elements. Try to congratulate your child for his/her achievements, be just with every child, draw an elder child in the youngest one's upbringing and make his/her responsible for keeping peace in the relationships, but teach a younger child to be respective and friendly towards his/her elder sibling.