how about you change the version of your minecraft to one of the snapshots before you stop playing, that way if your brother is not very observative he will start up the game and try to join a server, but it wont work. Or just log out of your account when you stop playing. Also how many profiles do you have in the bottom left of your minecraft launcher?(I have 3- one with optifne, one with current mc, and one with alpha v1.1.2_01)
weevil, its the bottom right corner of the launcher, u log out, and only log in when ur on, that way ur brother cant get on (unless u gave him ur password, in which case, change the password)
No sorry. It's a waste of time for most of us to type in the password, and if you share an account with your sibling, make some agreements on which mods/server he can use/go on. And if he just goes on your account without asking, just logout the next time. Because it's your account, and thus your responsability.