For life to exist on any planet, the main requirements are temperature range, and mass of the planet. All the other planets in our solar system are either too cold or too hot because of distance from the sun. Size matters because it must have the right size to keep gravitational force large enough to keep air from escaping.
Our solar system is part of the milky way galaxy. There are literally millions of suns in our milky way galaxy. On top of that there are millions of galaxies in our universe. Some scientists claim there are many more universes out there.
What it boils down to is this. We have no clue on the exact number of planets out there similar to earth. We do not have telescopes strong enough to detect every sun, much less every planet, in the universe. The distances are just so vast between solar systems and galaxies. The distances are measured in light years. Light travels 186,300 miles per second, so how many miles does it travel in a year? It is an unimaginable number = 186,300 x 60 x 60 x 24 x 365! I bet your calculator can’t even display the result. That is just ONE light year.
Now consider this... the closest galaxy to earth is the Canis Major Dwarf Galaxy and it is 25,000 light years from us! Even if we had a machine which can fly at the speed of light, it will require 25,000 years to reach the nearest galaxy!
My conclusion is that there are Gazillions of planets in the universe and life exists in at least 1% of those planets. But have no fear, they are just too far away to fear any invasion.
With the word "universe" meaning everything that exists, how can there be more than one "everything"? It defies logic.