The 21 jewel chests - Twist your Brain

Puzzle:

A wealthy King divided his riches between three sons. He said, "I have 21 identical, equally large chests - seven of them are completely filled with gold coins, seven are half-filled with gold coins and seven are empty. Can you divide these 21 chests among yourselves without taking the gold coins out of them, so that you all have the same number of gold coins and the same number of chests?"

Answer:

Each son recieves three and a half chest worth of gold as follows:

One full chest, five half full chests and one empty chest.

Three full chests, one half full chest, and three empty chests.

Three full chest, one half full chest and three empty chests.