Missing pieces

The story of the one and only avatar wasn't completely accurate.
To be probably be balanced, there are four avatars.
One per nation.
Two boys, two girls.
Three avatars left.
Four friends found over and over throughout their lives.
But the story got lost after the war started, the stories of multiple avatars became a fool's story. But as Aang gets closer and closer to returning to the world, the spirit energy used to keep him alive is returned to the others.

Compelteish but might add to it, open to suggestions!