YOU SAID:

My mother's mother's mother is my grandmother's mother.

INTO JAPANESE

私の母親の母親の母親は私の祖母の母親です。

BACK INTO ENGLISH

My mother's mother is the mother of my grandmother.

INTO JAPANESE

私の母の母は私の祖母の母です。

BACK INTO ENGLISH

My mother's mother is the grandmother's mother.

INTO JAPANESE

私の母の母は祖母の母です。

BACK INTO ENGLISH

My mother's mother is the grandmother's mother.