YOU SAID:

My mothers brothers sisters son is I

INTO JAPANESE

私の母の兄弟姉妹の息子は私です

BACK INTO ENGLISH

My mother's brother and sister's son is me

INTO JAPANESE

母の兄と妹の息子は私です

BACK INTO ENGLISH

My mother's brother and sister's son are me

INTO JAPANESE

母の兄と妹の息子は私です

BACK INTO ENGLISH

My mother's brother and sister's son are me