I was wondering if two different people can be logged into the same Gmail account at the same time.
And the answer is Yes ! two different people can be logged into the same Gmail account from different computers. Both accounts are semi synchronous, for example, lets say you get a new mail, then it will be simultaneous notified in both the accounts, where as if you delete any mail, then only a forceful refresh will update it in the other system.
This post teaches you how to see who else was logged into gmail your account other than you.