As a nonborn, it's possible that he had a nonoperant mother. The poster (I think it might have been Marina Drobnic) suggested that Aiken might not have only his biological father, Davy MacGregor, to thank for his massive metapsychic armamentarium.
At the time, Magnificat was not yet out, so we didn't know for sure that Diamond Mask's body was obliterated with Jack's. She clearly did not donate eggs to the metapsychic rebels, but is it possible she donated them to the Milieu? Since she couldn't have children with Jack, this would not seem that farfetched.
I suggested once that Luc might have donated sperm to the Milieu (how's that for GaySpermBank.com? :-D), and if he had, it would be quite interesting what an in vitro progeny of Luc and Dorothea might be like.
In any case, Aiken's biological mother could have been one of the Rebels, too - say, one of the Remillard cousins who donated an ovary. I suspected Madeleine at one point.