My comments and criticisms are that they are way too cute! What absolutely perfect color - this is a real keeper, as are they! This will be a wonderful photo for the two of them when they're all grown up - wonderful memories in this one.
OK, here is one criticism. You can see I love this picture. How could I not? But if you get another chance, and you will, try to get each boy's arms in the whole photo...rather than cutting off your younger son's arms. Believe me, I know that is not always easy or even possible.
In this case, I'd crop up a bit so we didn't actually see your younger son's arms. See what you think. It's just a suggestion. You'll probably have to come down a bit from the top, too, to balance it out properly.
BBW, I had the same thoughts about the cropping. I do enjoy this picture (one of my favorites - but I'm a bit biased). This shot was out of the camera (.JPEG) on my GF1/20mm Panny. I hadn't processed it (lack of time!). Another concern I had is that my older son was just slightly out of focus. Just an aperture change, I know.
Thanks so much for the kind words and the advice. It's the only way to improve! Did I mention that I love this community?!