You know that you are only trying to make sense of a story that dosn't really have any, right? All those questions you all have probably wasn't even considered when the story was written. But, I still blame the editors. They really need to start doing their jobs at some point.
~Epidot (Just blowing off some steam).
You are right, but one can also argue that since Harry and Lily were exposed to very different drugs/formulas than Norman, that the results to them and the baby were also different. But that should have been mentioned in the comic.