This was my exact thought. Chimerism happens in animals and in humans! I remember a court case where the state was trying to take a mother's child away because it showed that she wasn't the mother. However, upon further investigation, she had 2 different sets of DNA and 2 of her kids took one set and the other child took the other set. Seems plausable that this could have happened. A set of twins (one champagne, one lesser/pastel lesser) fused VERY early on (within days of fertilization) and it hatched out a visible chimera!
I would DEFINITELY hold that boy back and breed it to a normal. If it is a chimera, you should get champagnes and lessers. That will be a cool project to watch!