Depends on what kind of information you're looking for. Hiring an expensive
private investigator to dig up information on close or distant relatives is one thing.
However expecting them to uncover and elaborate on confidential medical records is quite another given our HIPAA laws regarding privacy. Even in the event people have direct access to such medical records as a part of their own employment. Keep in mind that not everyone is "up and front" about their autism. In essence what you are asking may be skirting along the edge of the law depending on various circumstances.
"Snooping on healthcare records of family, friends, neighbors, co-workers, and celebrities is one of the most common HIPAA violations committed by employees. When discovered, these violations usually result in termination of employment but could also result in criminal charges for the employee concerned."
The Most Common HIPAA Violations You Should Be Aware Of