Plato states in the Timaeus that every planet, star, etc., is inhabited, because God is God of life. But this does not imply that their life is like us. Early Christians thought it was better to baptize in "living water", by which they meant "flowing water", so that culture stretched the meaning of the word "life" quite a bit. Another consideration is that there is not proof that there's anything out there, planets, stars, anything like we think it is. We could all be being fooled by what we have learned in school.
What I can state for a fact, is that about 10 years ago the SETI program released a public statement, saying that although they had not checked the whole of space for intelligent life response, they had checked enough of it, that mathematically, it was almost impossible that any life like ours would ever be found. This statement says that our own science has proved that our own science is wrong about expecting inhabited planets.
If you want some more alien life to look at, how about angels? You could look at demons, but I don't suggest looking too long. Then there are powers, principalities, seraphim, cherubim, ophanim, etc. These were all created by God, most do not live on earth, and they are not human. Maybe the entire idea of alien worlds is just a natural response to having denied God for a long time, and missing some of the life He created in the spiritual realm.
