Boy, you sure ask a lot of questions that directly or indirectly hint at curiosity about guys wanting to be with other guys, don't you?
Not that there's anything wrong with that.
EDIT: OK, maybe not that many. I had just looked at your question about being with a girl and another guy, so it just seemed like a lot in a part of the forum that is pretty dead these days...
And now to address your question, since my original reply was a bit jack@ss-ish...
As someone with a science background, I would say that the answer to your question - the way you phrased it - is no.
Gender is (usually) a one-or-the-other phenotype.
Sexual reproduction is a heterosexual activity.
But studies have consistently shown that sexual
attraction/arousal is not an either-or, single-gene trait. It is likely highly polymorphic with
most of the dominant alleles being for 'heterosexual' tendencies (as one might expect given the relative survival advantage of those alleles), with the result being something like eye color. Eye color is a polymorphic trait which - if I recall correctly - is controlled by at least 6 alleles.
And there are probably far more 'shades' in human sexuality than there are in eye color.
So I would say no. If looking at a guy arouses you, that does not mean that you are "gay." It just means that the real world is a lot more gray than black-and-white, that's all.