I have learned that the Father and the Son are two individuals who look exactly alike and Christ is identifiable by the marks of His wounds. I am confused because I thought that we will still essentially look as we do now, but Christ is a child of God as we are and we are His brothers and sisters ... So, I guess I'm wondering why they are identical and why we will or will not look identical as well? 

The Apostle Paul declared that Christ is the "express image" of the Father (Hebrews 1:3) I would venture to theorize that the Almighty, our Heavenly Father, may have begotten the spirit assigned to become His Only Begotten Son in his likeness in order to indicate the unity or "oneness" that would forever exist between the two of them.

In our case, my current opinion is that our pre-mortal spirits probably did not look exactly like our current mortal bodies--that is, did not have the same facial and physical features. I suppose our pre-mortal spirits would have the facial and physical features of our Heavenly Parents.

For the time being, consider these words from the Prophet Joseph Smith:

"... the spirit is a substance; that it is material, but that it is more pure, elastic and refined matter than the body; that it existed before the body, can exist in the body; and will exist separate from the body, when the body will be mouldering in the dust; and will in the resurrection, be again united with it." (Teachings of the Prophet Joseph Smith, p. 270)

I've always been curious about the prophet's use of the term "elastic" when referring to spiritual matter. So, I wonder--remember that this is a personal conjecture with no concrete basis in revelation; it's just an intellectual exercise--I wonder whether the bodies of our pre-mortal spirits during their long association with our mortal bodies actually change some of their features and are changed into a combined likeness of the heavenly and the earthly. Then, in the resurrection, our bodies would be a combination of the facial and physical features of our earthly parents enhanced by the facial and physical features of our Heavenly Parents. For me, that would explain why Mary Magdalene and the two disciples on the road to Emmaus failed to immediately recognize the resurrected Savior.

So, according to this conjecture, we could have some measure of "likeness" or similarity with the Father and the Son, but at this point I am unable to tell to what degree.

One day in the future we'll find out whether my supposition is right or wrong.