YOU SAID:

My uncle parties with his sisters friends brothers cousins step brothers best freind

INTO JAPANESE

彼の姉妹の友人兄弟いとこの私の叔父のパーティー

BACK INTO ENGLISH

His sister friend brother cousin my uncle party

INTO JAPANESE

彼の妹の友人の兄弟いとこ私の叔父パーティー

BACK INTO ENGLISH

His sister friend brother cousin my uncle party