YOU SAID:

My brother better not peek at my stuff.

INTO JAPANESE

私の兄は私のものを覗き込むほうがいい。

BACK INTO ENGLISH

My older brother should look into mine.

INTO JAPANESE

私の兄は私のことを調べなければならない。

BACK INTO ENGLISH

My brother has to look over me.

INTO JAPANESE

私の兄は私を見なければなりません。

BACK INTO ENGLISH

My brother has to see me.

INTO JAPANESE

私の兄は私を見なければなりません。

BACK INTO ENGLISH

My brother has to see me.