Well it's easy, unless life was specially created here and only here chances are there is life elsewhere in the universe, Billions of galaxies, with billions of stars, many stars we already found in our own area with planets, and multiple planets/moons here in our own solar system with possible life, or had life at one time...chances are we arn't alone.
Now the issue to me is how common/rare is intelligent life.
First you have to have a planet that bacteria type life evolve/form, then have the planet support anything bigger. *one of saturns moons likly has nothing higher then bacteria, or mars right now*
If there is anything bigger then bacteria, does higher intelligence ever evolve, there are quiet a few intelligent animals here but only one human race.
If intelligent life forms evolve, are they a species taht could evolve abilities to use technology enough to leave the planet? Look at ravens and other highly intelligent animals on our planet, is it likly even with their intelligence that they eventually evolve the ability to use technology.
If the right type of intelligence and body structure evolved, are they on a planet capable of supporting advanced technology, you could have super highly intelligent mermaid like things on europa but being under water, and under ice is there any technology thaty could make to allow them to leave there?
Among other things, but a thought I had a while ago for how rare intelligent life capable of travel be. But in the end, if life is likly in our own solar system, then what about else where? I don't know how common or if there are any other species like us in the universe, but some form of life is likly.
