I don't want to tell you how to run your life. But if it were me i would punch him in the head over and over again and tell him to get his own fucking life. Like your privacy should not be in jeopardy because of your little brother.
-MBP
you need 2 hands to type your new password in... this will make your brother look at your right hand while you type 12345 with the number pad. and with your left hand type a letter before hand so your new password would be like a12345
see how long it takes him to crack it... it should be fun for you. if he does crack it add another letter!