Here's an amazing story abot a man who didn't know either of his dead biological parents' names, identifying both through high and low tech means.
Wall Street Journal 
MAY 2, 2009
Richard was an adopted child.
The younger Mr. Hill was quickly able to learn who his biological mother was. But cracking the identity of his birth father -- shrouded in coverups, lies and false trails -- took 26 years. In the end, Mr. Hill solved the mystery with the help of sophisticated DNA-based genealogy tests.
About 13 years later, in December 2006, a friend mentioned that he had used an online service, called Family Tree DNA, to trace his genealogy. Mr. Hill sent a cheek swab to the Houston company. It then compared several of his DNA markers on the Y chromosome to the DNA profiles of thousands of other men who had provided DNA for genealogical testing.
He got lucky. Based on a comparison of 25 DNA markers, Mr. Hill happened to get one perfect match. It meant that there was an 85% chance that he and the matched man shared a common ancestor within eight generations. More to the point, it suggested that there was a strong chance this man had the same last name as Mr. Hill's biological father.
 In April 2007, Mr. Hill wrote to one son of each of the Richards brothers, entreating them to be tested. "...That is the only way I can solve the central mystery of my life," he wrote. They all agreed. Mr. Hill paid a total of $750 for the five tests.
Unlike paternity testing, sibling DNA tests are never definitive. All they can measure is a level of probability that two people are full or half siblings. By two measures, the Genetrack test showed that Douglas Richards was the brother most likely to be Mr. Hill's father. Because of that and other evidence, Mr. Hill was sure his quest had ended. "I have an incredible sense of relief that I found him," he says.
http://www.wsj.com/article/SB124121920060978695.html