I think you misunderstand the Big Bang theory. According to the generally accepted Big Bang theory, it did not occur 'in' the universe, but it happened and 'created' space.

Think of it this way - the universe wasn't a big empty room inside of which the big bang took place. Prior to the big bang there was no space. The Big Bang created the room.

However, leaving that aside, it is not unreasonable to assume that somewhere else in the universe there may be other forms of more (or less) advanced life.