I suppose fair would be when all parties get equal treatment/amounts be it good or bad...but that would also imply that all parties involved are equal as people...should a child get an adult amount of food when it will not all be eaten? Should the drug addict be given money and food stamps when they will not spend it wisely? And like you said, who judges? Fair could exist but only as a theoretical scenario. It still shouldn't stop us from teaching our children though...we try to teach them what would be ideal and hope for the best I think.
Like anything else, equality of status requires sense, rather than blind rule following for the sake of rule following, which is just empty and devoid of meaning or purpose.
Symphony for a seabird
You cannot put a big load in a small bag,
nor can you with a short rope,
draw water from a deep well.
Have you not heard how a bird
from the sea was blown inshore
and landed outside the capital of Lu?
The prince ordered a solemn reception,
offered wine to the seabird
in the Sacred precinct,
called for musicians to play
the compositions of Shun,
slaughtered cattle to nourish it.
Dazed with symphonies,
the unhappy seabird died of despair.
How should you treat a bird?
As yourself or as a bird?
Ought not a bird to nest in deep woodland
or fly over meadow and marsh?
Ought it not to swim on river and pond,
feed on eels and fish,
fly in formation with other waterfowl,
and rest in the reeds?
Bad enough for a seabird to be surrounded by men
and frightened by their voices!
That was not enough!
They killed it with music!
Water is for fish, and air for man.
Natures differ, and needs with them.
Hence the wise men of old
did not lay down
one measure for all.