The preferred marriage in Arab society is with the Father's Brother's Daughter, and this was the case for Saddam's daughters, who married the Kamel brothers -- who then defected and unwisely returned to be offed. So they were nephews, too. They are all al-Majids, like Saddam, and everybody has the Y-chromosome of Saddam's paternal grandfather.
The only trick is that of course there are fewer markers on the Y, and it might be harder to determine initially. But if we get the body, we certainly will be able to confirm. You will remember the same technique was used to determine if Jefferson fathered any of Sally Hemmings's children, but there was an inevitable ambiguity because it could have been the sons of his brother -- same deal