Wonderful portraits of the boys indeed. But, as said, the white balance is off. Too blue-ish (and perhaps a bit too much green but that's difficult to tell without correcting the blues). You could use eyes or white on ball. To get a less harsh effect (especially shadows on the wall) you could flash vis ceiling or another reflecting object. You could also use a softbox on the flash or just a piece of paper if you use the built-in flash. Experiment without loosing the boys' patience. ;-) If you can't, move them a bit forward from the wall/door. This will blur background too.
If you see clear whites on your computer display, the colors are off on your display. Calibration helps.
Usually you can use Nikon's auto WB. Otherwise you could try the flash WB.
Did you correct WB and exposure in post-processing or in-camera? What settings/setup did you use?