No, here are the autopsy rules for TN:
38-7-106. When autopsies authorized — Notice to next of kin — Donor eyes and and eye tissues. —
(a) A county medical examiner may perform
or order an autopsy on the body of any person in a case involving a homicide, a suspected homicide, a suicide, a violent
, unnatural or suspicious death. When
the county medical examiner decides to order an autopsy, the county medical examiner shall notify the district attorney general. The district attorney general may order
an autopsy in such cases on the body of a person in the absence of the county medical examiner or the failure of the county medical examiner to act. The authority ordering the autopsy shall notify the next of kin about the impending autopsy if the next of kin is known or reasonably ascertainable. The sheriff or other law enforcement agency of the jurisdiction shall serve process containing such notice and return such process within twenty-four (24) hours.
Since there was no autopsy, the next of kin was not notified.
In the case where there is a will, it may state instructions on procedures relating to next of kin. Next of Kin is usually closest living relative in the state.
When you mean they i assume you mean the state, they would verify based on a claim which would be investigated.
I don't know why any blood or tissue samples would have been taken, or if they still exist. You said this was a while ago, these may have been destroyed if they were taken. You could ask, which you said has not gotten you very far, petitioning for a court
order I don't think would be effective, because your really not stating a controversy, just that you want to see them, if it was part of a lawsuit or criminal case, it would be different, as I know the medical examiner is not obligated to give access biological samples, if they even exist.
This case is complex and a full investigation would require a lot of footwork, you may wish to consult a private investigator in your area who could access the records, make the phone calls, go to the offices, this is really the only way to know for sure. I'm just trying to imagine how it might play out, but it's hard to do over a computer
I hope i at least gave you some insight, I am sorry for the loss of your brother and the stress this must be causing you, you have my sincere condolences.