Dear davenanswer

If his brain trauma was severe and blood supply to the entire right hemisphere is cut off then this can be a possibility. Another reason is that his right brain is not developed due to congenital defect. I would bet the second is the most probable cause. If the first one is the cause then he would have some problems in his left brain as well. Then the child cannot be normal.

What is the prognosis?
Human brain has remarkable capacity to adapt to new situations, especially in early childhood (neuronal plasticity). Therefore, if the child does not develop any further complications i would say that he will develop normally. However, he might experience some cognitive problems in his later life, but overall he will lead a normal life.

In fact, there are surgeries performed in extreme forms of childhood epilepsy, where an entire hemisphere is removed (Hemispherectomy). But these children develop normally with minor educational problems in later life. But overall the prognosis is good.

Usually left brain does the bulk of work in normal humans. It is responsible for speech and language. Therefore, intact left brain would be another good prognostic sign.

But I cannot predict the future, he may have problems later on but above things are facts that I know .

You can do a Google search on Hemispherectomy and read about the case reports available.

Hope your nephew will get better