WORD OF THE DAY! 4/9/12.

sibling rivalry [sib-ling-rahy-buhl-ree]
noun
1. A type of competition or animosity between children, whether related by blood or not. Such competition is particularly intense between brothers and brothers, sisters and sisters, children of the same or near the same age, and between children with talents. It is an expression of the frustrations between children to compete for attention and to define themselves as being apart from their rival.

EX.  In the 2008 film Step Brothers, two middle-aged men compete for control of the household like children when their parents get married. Their sibling rivalry, a rivalry built on man-child stupidity, is the amusing crux of the film and the two principle actors, Will Ferrel and John C. Reily, pull off the ridiculous film with their physical comedy, crafted delivery, and legendary chemistry.

An even more interesting pair of sibling rivals are Marvel's Thor and Loki, who compete for their father's respect, the people's attention, and control of Asgard. While Thor would happily compete against his brother in a friendly rivalry, Loki takes their rivalry too far and makes himself a villain to win their struggle. The rivalry is complicated by Loki's desires to be the ruler of Asgard AND, despite his methods, earn the respect of his fellow Asgardians, especially his father and brother. It is this sibling rivalry that not only propels the 2011 film Thor, but also has propelled Loki into becoming the main villain in the upcoming Avengers film.

Speaking of sibling rivalry...

Apparently, Damian has a beef with Tim Drake.