If you think about the never ending size of space then it would make perfect sense to say that there is other life out there somewhere. If the Earth and our universe were created via the 'Big Bang' then what's to say that it couldn't have happened somewhere else millions and millions of miles away?
It's ignorant of man to think we are the only ones in the entirety of space. Even if we find living cells on another planet it's still classed as life and it would have to be classed as alien. Maybe there are full civilizations out there but so far away that they can't reach us and we can't reach them. Their could be Aliens out there that are simply not interested in communication with us because we are so primitive and basic compared to the. We still suffer from war, plague, famine why would a advanced race ever want to contact us?
Considering all of that maybe there are other humans out there, like i said before if we were created via the 'Big Bang' then maybe another 'big bang' happened somewhere else. Think about it, life must be out there somewhere. The real question is would they be interested in communicating with a basic puny race such as us?