I think there is a lot of info about the whole group at the CIA.
The Son of Frank Marshall Davis should not have been able to get DIA clearance..but he claims he did.
Why not? If he was "clean" himself, it wouldn't matter if his father was Julius Rosenberg, although I'm sure they'd take a really close look at FM Davis' son.
I do believe there is something in the Constitution about "no corruption of blood" even for Treason. See Art. III, section 3.