What is the thesis of the novel Founding Brothers?

First, Joseph J. Ellis's book, Founding Brothers, is not a novel. It is a non-fiction account of the interrelationships of various Founding Fathers over certain specific issues during the time of the creation of the United States of America. We refer to men like Washington, Adams, Franklin, Jefferson and others as "Founding Fathers" because they are from prior generations. But during their lifetimes, they were of the same generations just like brothers are. The book goes into several topics where the "Founding Fathers" had some strong differences of opinion and even fought amongst themselves in much the same way that brothers argue over matters within their families. The Founding Fathers were certainly not all of the same political mind, even though it might seem that way to us now.