Well it seems silly that would would be the only form of life in the infinite of space...

I think that there is a great probability of alien life forms to somewhere out there. Degree of development??? I dont know.

Ya why not ?

Yes.

well...actually no :D there isnt' even a proof that this alien felows live

It's not a matter of belief. Statistically speaking, the probability of there being at least on one other intelligent species someone in the universe is nearly certain. In the Milky Way galaxy alone, there are estimated to be over 300 billion stars. With millions upon millions of OTHER galaxies in the universe, it is currently estimated that there are 70 septillion stars in the universe (a 7 followed by 22 zeroes) visible from our telescopes. The maximum number of stars in the universe is unknown, and probably incalculable. It's possible there could even be an infinite number of stars. If even a forth of those stars is orbited by a planet, that is still a number of planets that is incalculable. And a tiny percentage of those planets is likely to have developed some form of life. So, given the sheer size and vastness of the universe, the idea that we could be the ONLY inhabited planet is statistically slim, if not impossible. Mathematics suggests that there has to be at least one other species out there in the vastness of space. While the vastness of space makes it quite likely that there are other species in existence, it ALSO makes it unlikely that we'll ever actually encounter any of them.

well not aliens anyway haha

It's not really a matter of "believing" in it. I find no reason to assume that other planets have no animal life.

I don't believe there is intelligent life in the universe. Certainly not as advanced as us, if there is any intelligent life out there.