Arguments between siblings are normal but if it results in frequent physical fights then there is a problem between them which should be resolved. But who will resolve the problem? Of course the parents because they have authority over their children.
1) Parent should try to explain to the children that why family matters and why good relations between them is necessary for the peace of the family.
2) Ask them about the issues they have with each other and try to create a win-win situation so that both will be satisfied without any further arguments.
3) Maybe they just want more space, then let them do so. If one sibling is interfering into the matters of other then he should be stopped.
4) The culprit among the children should receive some punishment through which he will realize that such behavior will result in unfavorable situation for him. For example cut down his pocket money, stop it for few days or just gift anything to others and tell him he will not receive any because of his behavior.