How to unlock my new iphone4s?

I know this may sound werid, but my brother has just got the new iphone5 and he said i could have his iphone4s. My brother is very stubborn and he told me if i can unlock it i can have it! I have always wanted an iphone as i have never really had a nice phone. My brother has a password in his phone and i don't know how to unlock it. He said that you have to use itunes but i don't have a itunes account. I made one ages ago for my ipod and i was wondering if i could use my itunes account for the iphone. I just need to know how to get his password unlocked on my itunes account without jailbreaking it. (i know this sounds like i have stolen the phone) but honestly i just really want my brothers old iphone4s. Any help please! I will be very greatful!

Plug it into I tunes (any account will do) and simply click 'restore' all data will be wiped including the password etc

Look http://osxdaily.com/2012/02/22/unlock-the-iphone-4s-with-gevey-sim/