Handling siblings who interpret equal treatment as unfair treatment

One child says it's unfair that their sibling gets more help with homework. The sibling says it's unfair that the first gets more freedom. Both are comparing the visible result, not the different needs behind it. I've tried saying ‘fair doesn't always mean identical,’ but that phrase has become background noise in our house. Has anyone found a way to explain age-appropriate differences without turning every decision into a courtroom hearing?