I recently caught up with Ken Penders at the San Diego Comic Con and this is the exact conversation: Me:
Out of all the Dark Legionaires that actually have been named, they are Sergeant Rykor (Knux 8), Xenin, and Syntar (Assasin "about" to kill Julie before Lara-Su stepped in). So if Kragok does have a son, it's gotta be outta those three legionaires!
Who said it was a Dark Legionaire? Maybe it's someone you've seen but that person doesn't realize he's a Legionaire. But I'll be fair, if it was a Dark Legionaire (and I'm not saying it is or isn't), it would be those three.
So there it is. Not sure if this helps, but it sheds some light on who Kragok's son may be.