quantum field theory - GUT that includes all 3 particle families into a large group?

Explaining SU(5) GUTs (using the first particle family as an example) in the last SUSY lecture 10, Lenny Susskind mentioned that there are at present no ideas how to combine simultaneously all 3 particle families into a large GUT theory. I somehow dont believe him, suspecting that he just didnt want to talk about this :-P...

So, are there any ideas around how to incorporate all 3 families into a larger structer?

If so, I would appreciate explanations about how it works at a "Demystified" level :-)

Answer

Jacob Bourjaily derives three Standard Model generations from an E8 singularity here and here. (See comments by Lubos, 1 2 3.)