The grandson of a grandson is the son of a son, also known as the son of a great-grandson, or the grandson of a grandson, or the great-grandson of a son. It's for the fourth grandson, called great-great-grandson. Great-great-grandson is called Sun Yuan in some places and Bang Sun in others.

brief introduction

China's legal relationship adjustment includes husband and wife, parents, children, brothers and sisters, grandparents, grandchildren, daughter-in-law, in-laws, son-in-law, legal parents, and other blood relations within three generations, such as "uncles, aunts, nephews, cousins, and so on".