lolololololol
lolololololol
Simply change the password through the Steam Community which pops up on opening of Steam.
If you can't find it try going to Steams official website and change your password.
If he has your password, he can change every aspect of your account, email, security question, with a couple clicks.
It's stupid to share a steam account with anyone but direct family members. Change the password and tell him to buy his own copy.
Reputation: 10I'm sharing one of my spare accounts with a friend. He won't hack it cuz I can trust him.