Agreed. I am surprised we don't see this more actually. A good PhD advisor can make a world of difference if s/he is working with a good student. Also, you maintain that connection throughout your career and tend to work together (even if informally). Seems like Rabi knew what he was doing.
Turns out there's a few other academic families (that's PhD advisor lineage, not genetic) that have received >2 Nobel Prizes.
Of note there are 2 other direct Nobel-to-Nobel lineages of 3 generations:
1) I. I. Rabi -> Julian Schwinger->{Ben R. Mottelson, Sheldon Lee Glashow, Roy Glauber, Walter Kohn, Samuel Chao Chung Ting}
2) Eugene Wigner->John Bardeen->J. Robert Schrieffer
Rabi seems to be a good academic grandfather.
source: http://en.wikipedia.org/wiki/Academic_genealogy_of_theoretic...