If the cbc count is normal, you dont have alot to worry about as leukemia affects the white blood cell count.
Has your nephew been feeling more tired than usual?? Losing weight no matter what or how much they eat? Look pale?
I really hope that he doesnt have leukemia because it does take alot out of people in the recovery process.
Always remember, even if he does have leukemia, it is curable!!
Update us on your nephew when you get a chance! Goodluck!