From the FB post:
"And so now they are going to be getting 5 more samples from Jason's father's children with the male dna being the most important because he is a son and also a male as Jason was."
https://www.facebook.com/GratefulDoe/posts/959966590743628
That reminded me of the DNA matching in the case of Robert DeSalvo, the Boston Strangler, so I reviewed some of the articles I'd read a couple of years ago. The circumstances are different, but this snip might explain why they are interested in testing a male child of GD's father.
"The match was possible because of tests that zero in on short tandem repeats (STRs), which are patterns found on DNA strands. Forensic scientists use a specialized test that focuses on male (Y) chromosomes. Y-chromosome DNA comes from fathers who pass their Y-STR DNA profiles to their male offspring. Barring a mutation, the profiles remain unchanged. Every male in a paternal lineage has the same Y-STR DNA profile. This includes fathers, sons, brothers, uncles, nephews and a wider group of male relatives, even out to third and fourth cousins."
http://nij.gov/journals/273/pages/boston-strangler.aspx
As I understand it, the above won't yield a match to one particular individual, but can narrow the possibilities to a group of male subjects from the same paternal lineage. So combined with the results from the mother's DNA, a positive result would close in the circle. I *think*.
