As teens search for their individual identities, they can often begin to feel competitive and argumentative with their teen siblings. Rather than always stepping in to end these disputes, parents can better use these opportunities to help their teens learn coping skills, compromise, how to appreciate another's point of view, and negotiation. In other words, help your teens to learn to navigate and resolve their issues between themselves.
When sibling teens do start fighting, it's best for parents not to get involved as long as there is no potential for physical harm. If parents step in and "fix" all teen sibling disputes, it's likely that the teens will never learn to resolve differences and they could become too reliant on their parents. Also, if a parent does get too involved, it can be difficult to keep from affixing blame to one teen or to resist the temptation to take sides. When this happens, the parent can often increase the level of sibling rivalry, rather than resolve the argument.
What parents can do is to coach their teens to take constructive approaches to resolving differences, enforce house rules evenly and consistently, and listen to them as the teens share their issues and feelings. Since parents will better life experience on which to draw, and therefore may see some easy or clear solutions, they can make some pointed suggestions; but it's a good idea to let the teens reach the conclusion on their own. If the argument is particularly heated, parents might want to separate the teens to allow a cooling period. In other circumstances, parents might need to remind the teens not to name-call or to use inappropriate, unhelpful language as they argue.
In order to limit the occurrence of sibling rivalry and arguments in the first place, parents should make sure to spend quality, positive time with each teen individually. Each teen should feel loved and valued, separate from his/her sibling. In the same vein, parents should celebrate the successes (including best efforts) of each teen.