I said this all once here, but here it is again, just as pertinent:
I had a conversation and a dream about this just last week. No joke. And this time your tin foil hats won't help you.
I think the technology is there for the government to take genetic samples from everyone in the U.S. armed forces, and thereby build a database in which they could match any found genetic material by gene clade, and describe your relationship, and triangulate your placement in the larger family tree, with a reasonable degree of certainty.
More simply put, a hair or skin flake on the ground could tell them who your brother, cousin, second cousin, uncle, all in different branches of your family, are. With that information it wouldn't be hard to find you.
Really, I'd be more surprised to find out definitively that this wasn't already in place.
Anyway, I feel a bit like a nutter saying it, but with enough computing power, we already have algorithms that do almost, if not, all of this.