YOU SAID:

i heard that she split up with her boyfriend because he cheated on her with his sisters best friend

INTO JAPANESE

彼女が彼氏と別れた理由は、彼氏が妹の親友と浮気したからだと聞いた

BACK INTO ENGLISH

I heard that the reason she broke up with her boyfriend was that he had an affair with his sister's best friend.

INTO JAPANESE

彼女が彼氏と別れた理由は、彼氏が妹の親友と浮気したからだと聞きました。

BACK INTO ENGLISH

I heard that the reason she broke up with her boyfriend was that he had an affair with her sister's best friend.

INTO JAPANESE

彼女が彼氏と別れた理由は、彼が妹の親友と浮気したからだと聞きました。

BACK INTO ENGLISH

I heard that the reason she broke up with her boyfriend was that he had an affair with her sister's best friend.