I am guessing that you are using Ubuntu Linux. If so I can help you there.
Even though I am almost a newbie on Linux and Ubuntu I have figured that one
out.

Go to System next to Applications, then Administration and then go down to Users
and Groups.

This page you unlock with your password and then you can add a user. Just like
yourname/home it will be hisname/home a different directory.

Now I have no idea if he can view your directory or not. I have never tried to
log in under user1 to see if I can see my home directory? But that is how you
add a user.

Now you can add your brother and see if you can view your directory from his? I
have to try that with my user1.