If you know ANYTHING about our Universe, you'll know that the chance we're the only life is ridiculously miniscule.
Think about it this way: We are in the Milky Way galaxy, a galaxy with anywhere between 200,000,000,000 to 400,000,000,000 stars in it.
There are estimated to be at LEAST 100,000,000,000 - 170,000,000,000 galaxies in the known Universe. Each with, we must assume, an average of 300,000,000,000 stars.
So that's 135,000,000,000 multiplied by 300,000,000,000, and that's how many stars are in our Universe.
4,050,000,000,000,000,000,000,000 stars in the known Universe. How can we be the only sentient life?
Multiverse theories are based on solid scienific research, maybe not a reality, but a definite possibility. So if there are multiple Universes, multiply 4,050,000,000,000,000,000,000,000 by however many there are to get the approximate amount of planets.