Thanks for contacting us again. I expect the adoption was sealed and remains completely confidential to this day and your brother would have to go to court to have it unsealed to gain access to his birth information. You can consult with an adoption attorney for more information. I'm located in Virginia, but I'm not a law expert.
You can also check out this site: http://www.gsadoptionregistry.com/virgina/19701979virginia.html
They help find information (if the birth family is willing to cooperate). In any event, it won't hurt to register with them.
You can also check this board: http://www.eboards4all.com/74706/index.html