In definition, sibling rivalry is when one sibling or more compete with one another or try to emulate each other .Rivalry is different from fighting. Sibling relationships can be a key to rivalry. An intense relationship includes love and hate, play and fight, and the teasing and mocking of each other. Siblings usually have a very harsh relationship when they are young. As they mature, they become better friends and start getting into fewer and fewer fights .Brothers and sisters sometimes work together to get through jams.
Aggression is very frequent in sibling relationships.
Plus, not all rivalry is negative. Birth order greatly affects the relationships between siblings. First children tend to accomplish more than their siblings do because their parents expect more of them. All children in a family behave differently because of the way they are or were treated by their parents and others. The first child is very bossy to younger sibs, and has strong beliefs about what is right or wrong, and how his younger sibs should behave.