Another big fan of the movie, actually, just watched it on saturday 🙂
The first time that the doctor spoke, it sounded an awful lot like his father. There were also some other clues that made me think that as well -
One - the "nice piece" comment during the urine test. Just the doctor commenting that he wished he had ordered one himself sort of gave me this impression that the doctor was implying "He sure as hell didn't get that from my side of the family".
Two - the comment about the doctors son having the same desires as Vincent sounded awful suspicious.
Three - At my estimate, Vincent left his family for at least 10 years. If you hadn't seen someone in ten years, there is a chance that you might not recognize them again.
But, on the other hand, there were two very obvious factors that disuade me from thinking that the doctor was Vincent's father.
One - Age. Simply put, the doctor looked too young to be his father.
Two - If being of the "Genetic Elite" was that big of an issue in getting placement, wouldn't it be a little odd that his father, a "God Child" was a doctor at one of the most highly reguarded science centers?