YOU SAID:
james likes his bestfriend's brother
INTO JAPANESE
ジェームズは親友の兄が好きです
BACK INTO ENGLISH
James likes his best friend's brother.
INTO JAPANESE
ジェームズは親友の弟が好きです。
BACK INTO ENGLISH
James likes his best friend's younger brother.
INTO JAPANESE
ジェームズは親友の弟が好きです。
BACK INTO ENGLISH
James likes his best friend's younger brother.
That didn't even make that much sense in English.