For me, the answer for that is unknown. Aliens, although we cannot see them, it still possible that they exist but although we can see many proofs, like UFO sightings, alien pictures etc., it is still possible that those are "fake" or just an illusion or something like that.
But for me, just for me, aliens do not exist, and that is because I believe in God. God do not made Aliens right? Although we cannot see God, he guides, helps, and loves us. Although we cannot see Aliens, do aliens guides, helps, loves us? nor attacks us? No, right? Hahaha.
Alam ko nakakatawa, pero para sa akin, walang aliens. Ewan ko nalang sa NASA kung may alien sightings ba sila o kung anuman.