Can be either. Some people have awful trouble getting their autistic child to have much sleep, other lucky ones( like me) have an autistic child that goes to sleep and bed no problem.
Hi - Yes there are a number of kids with autism who do have problems letting down and falling asleep (and others don't!). Some pediatricians are reccommending Melatonin to help regulate the sleep cycle but two is rather young I think for this. Your nephew may be more in a typical two year old sleep difficulty time.
I would strongly rec'd that your brother or sister talk to the pediatrician about the problem and see what they suggest.