Yes God did tell us about everything He created, He even got Adam to name them and there were no Elves or Fairies among them. He told us He created Angels and Demons (or Aliens) as some prefer to call them.True.. BUT who is to say that there is not life on other planets? Why put life on only ONE planet, and leave the others devoid of any other life form?
If Earth is the only planet with a life form on it, then the other planets were created for a useless purpose..
He told us He created the stars and planets for us to admire and explore, He never said we have cousins out there. He would have told us if He created them.
We haven't even learned everything about our own planet and all the kinds of animals so we shouldn't worry about the void of space, it has nothing to offer except for beautiful night sky.