Was New York also the state in which he was residing at the time of his death? This matters because most of the law that applies here is state law. Also, why do you want the medical records?
As gemini47 pointed out, the federal Health Insurance Portability and Accountability Act (HIPAA) has a privacy rule that applies to most medical providers that prohibits disclosure of a patient's medical records to third parties without the consent of the patient except in certain limited circumstances. A child simply wanting to see his/her parent's medical records isn't one of those exceptions.
You could get them if you got a court order or were otherwise entitled to get them in discovery, but that means you'd need to be a party to a lawsuit in which those records were relevant. There is nothing in your post that indicates why you want these records, and that's important. Are you just curious as to what his medical condition was? Are you just interested in learning what the cause of death was? Or is there something more to it?