Considering the size of the entirety of space, yes. Do they exist in the capacity of what most people think of when they think of aliens? I don't know. To me, some microbe on a far off planet counts as an extraterrestrial, that certainly exists within the vastness that is space. Is there another life form that is within a moderate technological proximity to the human race and its accomplishments? I do not know. We'll just have to see as time goes on.