Who is Hyung-gu from A Single Shard and what is their importance?

Hyung-gu was Min's son. He died at the age of twelve, leaving Min heartbroken. When Tree-ear asks Min to train him, Min refused based on the tradition that potter's pass their skills down to their sons. He changes his mind, however, after Tree-ear returns to Ch'ulp'o after the death of Crane-man. At this time, Min and his wife take Tree-ear in and change his name to Hyung-pil.