age is a big factor in determining the severity of sibling fighting. For example, a 5-year-old hitting their sibling over a toy may be considered developmentally appropriate, but a teenager ...
People are more important than things. It seems so logical. Of course, we believe people are more important than things.
Siblings often fight over toys as well as attention from parents. It helps that they all like to play with different things, but they still often want what the other one has. This is normal.