YOU SAID:

my daddy is my sisters son

INTO JAPANESE

私のパパは私の姉妹の息子です

BACK INTO ENGLISH

My dad is the son of my sister

INTO JAPANESE

私の父は私の妹の息子です

BACK INTO ENGLISH

My father is the son of my sister

INTO JAPANESE

私の父は私の妹の息子です

BACK INTO ENGLISH

My father is the son of my sister