Biological family for boy born 6/47 or 9/47 on air base in South Dakota

Hi, I am looking for my birth grandparents or aunts/uncles. All I know is my father was PROBABLY born in June of 1947 on an airbase in South Dakota. His birthdate in Iowa was September but a neighbor told me they did that to match my adopted grandfather's birthday. My father refuses to search but I have an autistic nephew and would like to know if it is a family trait. The neighbor also told me that she heard my father was the youngest of 6 or 7 children. Any information would be appreciated.