This definitely sounds like a legitimate issue to me, not just a minor delay or something similar. I would definitely have him evaluated (this is free through the public school system even if he doesn't attend public school).
He definitely could have sensory integration issues. This can be a diagnosis in and of itself or it can be a symptom of something much bigger (like autism). The hyperactivity can also be its own thing or it could be the result of his senses being so overstimulated all the time.
I really couldn't possibly say anything for sure without seeing him for myself, but he certainly sets off enough red flags that in my professional opinion and evaluation is definitely warranted. This is not something that your sister can fix on her own.
