I should have been more specific in my question - the brothers commented to several people that the three main characters were based or partly based on three living people. Unfortunately, I can't go into more detail because I haven't been able to get in touch with one of the "possible" three people. If there is enough interest I'll give out more details. I'm looking for Chicago references - I'll say that much.
Regarding the earlier insights, I agree - the characters are definitely a Joycian amalgamation.
if you are looking for references in chicago, you will not find the answers unless you are willing to undergo some soul searching yourself. if you are, try the soul vegetarian restaurant on stoney island . perhaps you will be surprised.