The sibling who fought you at home and defended you at school is a deal you don’t get with anyone else.

Siblings run a private war and a public alliance, and the two do not contradict each other. Fighting at home is safe, because the relationship is permanent and nobody is going anywhere, while a threat from outside puts the household on one side instantly. You will not find that arrangement in a friendship. It is one of the few relationships where conflict is not evidence of a problem.

Remember the defending part next time you are deep in the fighting part. And do it in the other direction this week, even if you are annoyed with them, and especially if they are younger.