Searching for brother born 6/15/1972 at Dover Air Force Base Hospital

I am searching for my full brother born to John and Dal Asher on June 15, 1972 at Dover Air Force Base Hospital. According to my parents, he was adopted by a family living in Willmington, DE. I have searched with all the existing adoption agencies in the state at that time, and have been unable to find any record of his birth. I do have his birth certificate and various other facts. Please contact me if you have any information or can help me in my search. Thank you!