@Brandon9000,
From our human perspective it certainly seems far more than likely that there is life in the universe beyond that which exists on earth, but probability is not a rendering of actuality.
Personally, I do think that life is not limited to earth, but in a universe of near infinite possibilites, virtually anything is possible...including the earth being the lone bastion of life in the universe.
A child falls out of a third story window and is caught and saved by a man who years later has a grandchild fall out of a window and saved by a passerby.
The members of a church choir who religiously meet every Thursday night for practice all have a reason to skip practice one Thursday night. The night when the church's boiler explodes and anyone within it would have died.
We see these events as part of some sort of plan or the result of divine inteference, but in a universe of near infinite possibilities, such remarkable coincidents are easily explained by math.
Since the universe offers no reliance on anything we might think has to be, life throughout the universe is hardly a given.
As for the similarity of extra-terrestial life to life on earth, right now the overwhelming prevailing theory is that what we know as physics is a universal constant.
There is at least one certain function that all life must find a way to deal with: absorbtion and internal conversion of external energy.
To a lesser extent we can expect that life elsewhere must also find a physical response to biological imperatives of reproduction, and locomotion.
Life on earth has found two responses to the former and numerous responses to the latter.
On an earth-like planet, physics will limit the available solutions to the primary and secondary requirements of life.
Evolution on earth has not had anywhere near an infinite selection of responses from which to choose, and neither will life on an earth-like planet.
It is, of course possible that there is "life" on planets very much unlike earth that we will have difficulty recognizing (the "life as we know it" concept), but it's difficult to imagine that any life with which we have virtually nothing in common, will be anything other than a curiosity to encounter.
Should we ever find life on earth-like planets, my bet is that it will far more similar to life on earth than is generally supposed. Single cell life on earth, Mars or Planet 9 is not going to be drastically different; nor will whatever respective steps up the evolutionary ladder extra-terrestial life may take.
