Having a better understanding of why kids fight will help you better avoid conflicts in the future, as well as deal with those that do arise more effectively. With that in mind, here are some of the common causes of sibling conflict:

Personality differences

Research by Dr. Judy Dunn at Pennsylvania State University has shown that siblings who are temperamentally different when they are young tend to have more quarrels than siblings who are similar. So some kids may simply be more compatible towards each other than others.

Children may fight as a means of establishing their position

A lot of conflict involves children jockeying for position within the family and testing their place or their parents’ love. Dr. Lawrence Kutner points out that fighting with a brother or sister can be a way for children to try and determine the favored child in the family. Studies by sibling researcher Dr. Furman have supported this theory: Children who feel they are treated unfairly by their parents are more likely to fight with each other. (Kutner, 1996) This is one reason for all the fights over “firsts.” Who’s first to get a cookie, who gets the first kiss goodnight, who gets the first turn on the teeter totter, etc. It’s also behind fights over “more”: who has the bigger cookie, who has more marshmallows in their cup of hot chocolate, etc. Children merely use these things as ways of testing whose needs come first (and henceforth, who is more important) when it comes to their position in the family. It’s an instinctual, compulsive habit. They’ll constantly be watching for any signs of favoritism, and the more secure you can make them feel in this regard, the less conflict you’ll have over these issues.

Siblings fight to differentiate themselves from one another

In contrast, siblings may also fight as a means of differentiation – possibly one of the reasons why fights seem to be the most intense when siblings are close in age and of the same sex. (Kutner, 1996, p.161) They don’t want to be exactly the same, which by default means taking a contradictory approach towards things, something that is a recipe for conflict. Whenever you have two kids trying to go about things in 2 different ways (while proving how superior their way is to the other) this inevitably leads to fighting.

Displaced tension

In the same way that a husband may bring work stress home with him and end up taking it out on his wife and kids, siblings often experience stress from peers or from school that they take out on siblings. Maybe they’re mad at a friend and can’t punch him, so they punch a brother. Or perhaps a teacher yelled at them, and they can’t talk back to an adult, so they alleviate the situation by lipping off to a sibling. The fact that siblings are more familiar and permanent means you can do things to them you couldn’t do to others.

Sometimes a sudden increase in fighting between siblings is a way of coping with increased family tension. Kids will mirror adult emotions. This is why sibling conflict often becomes a bigger problem during a divorce or some other family crisis.

Boredom

Sadly, picking on a sibling can be a form of amusement. This is why you’ll often see an increase in fighting whenever children are bored.

Power struggles between siblings

“There is always a power contest involved in a fight. Equals don’t need to use conflicts as an opportunity to gain superiority.”

– Rudolf Dreikurs & Vicki Soltz (1964)

Just as a pack of wild animals will quarrel to determine which member has more power and authority over others in the group, siblings will spar back and forth as a means of determining their position and status in relation to others.

Fighting with siblings can also be a means of testing or exercising one’s power. In the same way that a toddler feels a sense of empowerment by pushing over a tower of blocks or otherwise dictating the state of their environment, siblings may feel empowered by their ability to goat or manipulate their siblings. This fact was reported very poignantly by one parent who says, “0nce while he was teasing him, I said, sort of sarcastically, ‘Boy, it’s fun to bug your brother, isn’t it? And he answered, ‘Yeah, it gives me power. I need it for my soccer game. ‘” (Faber & Mazlish, 1998, p. 128)

Sexual tension

Especially in stepfamily situations, kids may fight in order to counter or suppress sexual feelings they might have for one another. This can occur among preteens as well as teens, and sometimes among biological brothers and sisters as well.