I believe they do exist. The multi-verse is too large for us to be so egotistical to think we are the only form of intelligence. The Sumerian stone tablets have deep cosmic history. Everything was made of space dust, our bacteria that formed atoms were from stars so yes we too are alien imho. To think we are the only beings would be like being a galactic racist denning anything else should exist or something lol. just we cant see them doesn't mean they are not real.I have seen ghosts and spirit possession. I believe.