YOU SAID:

My sister has a friend who is also my sister and they are forty

INTO JAPANESE

私の妹には私の妹でもある友人がいて、彼らは40歳です

BACK INTO ENGLISH

My sister has a friend who is also my sister, and they are 40 years old.

INTO JAPANESE

姉には私の姉でもある友人がいて、40歳です。

BACK INTO ENGLISH

My sister has a friend who is also my sister, and she is 40 years old.

INTO JAPANESE

姉には私の姉でもある友人がいて、40歳です。

BACK INTO ENGLISH

My sister has a friend who is also my sister, and she is 40 years old.