内ない孫そん

noun

grandchild from one's son (especially the heir)

Refers specifically to a grandchild born to one's own son, as opposed to a daughter's child (外孫). Often used in contexts of family lineage and inheritance.

• 長ちょう男なんに内うち孫まごが生うまれて、家いえがにぎやかになった。

  When my eldest son had a child (my grandchild), the house became lively.

• 内うち孫まごと外そと孫まごでは、相そう続ぞくの扱あつかいが異ことなる場ば合あいがある。

  There are cases where inheritance treatment differs between grandchildren from a son and those from a daughter.