While there are no benefits to physical fighting between your children, there are benefits for them to learn how to handle the conflicts. these conflicts between siblings tend to be the back bone of why we deal with our peers the way we do. Siblings are usually our first attempts at socializing with non-adults. Your teens can learn these things through sibling rivalry:
conflict resolution;
why being fair isn’t always what happens;
how to deal with not getting their way;
and how to win.
It’s isn’t natural to learn these things through sibling rivalry. But, your teen still needs you to talk to him about the conflicts so he can work through the life lessons sibling rivalry teaches.
For instance, you want him to win with humility, not arrogance. That is character training and has to be taught. Role play with both siblings, allow them to work it out in a supervised setting and your teen will gain some valuable skills for later in life.