If you continue to have this issue, view the focus point in ViewNX 2 (it's Nikon's RAW viewing software). You can view where the focus point was this way. You can view a larger sample size of your pictures, and determine if the focus is slightly backfocused, or frontfocused, or just generally off. If you have issues, take the lens in for warranty servicing.
However, at f2.2, the picture seems decently sharp. As it has been said above, without a full sized image, it's impossible to say where your issue is stemming from.
My hunch is one of the two:
1) You need to stop down a bit to get the sharpness you want (simply a limitation from your aperture, not the lens). Possibly you need to pick a slightly better point of focus at f2.2.
or
2) Your lens is defective in some way. Either the focus is off, or it's not as sharp as it should be. At f2.2, my 35mm 1.8G (which is a defective one) is tack sharp when it does get the focus on. There is a shallow depth of field, however most of the two boys should be in proper focus if your focus point was the left eye of the boy on the right from my point-of-view (or his anatomical right eye).
edit -- One other thing: Did you do any edits before posting? You are shooting at ISO 200 and getting 1/4000 of a second shutter speed. You might want to drop that down to ISO 100, since you're maxing your shutter speed in that lighting at ISO 200 (assuming you didn't bump any exposure in software after).