Many people sometimes wonder if humans are the only sentient species in the universe. I thought about it multiple times, too. Here I present my thoughts about this from 2 perspectives.
For a lifeform to form on some planet in the space, a lot of conditions must be met. It requires a sophisticated ecosystem and climate. And even if other lifeforms exist, they would need to invent an ability to colonize other planets to ultimately encounter other lifeforms. To this date, humans haven't invented a way to expand beyond Earth, and I think, will never will, because it would require to design ways to transfer plant and animal life to other planets. And other planets in our solar system are just hostile to life.
As we know from Christianity, God created universe and humanity with a specific plan in mind. He intended humanity to live unspecified amount of time until Second Coming of Jesus Christ. Human life is a continious test of human nature, his affiliation to good or evil, which after death determines his ultimate fate. Extraterrestrial life was never mentioned in Bible, and it doesn't really fit anywhere into God's plans. If God were to create several lifeforms, he would need a reason for that, a destiny designed for each of those lifeforms.
All that leads me to think that we are alone in this vast universe. We are destined to live on one planet, and manage it carefully to avoid selfdestruction and extinction. I think we won't ever be able to colonize other planets, because it is an extremely complicated endeavour.