I'm not sure that focusing on founding fathers is terribly helpful, given the structural forces driving the European nation-states towards some limited forms of integration in the post-war period. See splendidly skeptical note on the role of federalist inspired "founding fathers" expressed by Alan Milward in his The European Rescue of the Nation State. For Milward, the driving idea was not federalism (overcoming the nation-state) but limited integration as a means of rescuing the nation-state. This passage from Chapter Six of his book captures the key point:
For a critique of the Milward thesis--namely, that European Integration represented an effort to rescue the nation-state rather than overcome or replace it--see Robert Bideleux, "European Integration: Rescue of the Nation-State," The Oxford Handbook of Modern European History (available on the course blackboard website).
Robert Schuman,
Jean Monnet,
Alcide de Gasperi,
Henri Louis Spaak
Konrad Adenauer.
Altierro Spinelli
One other figure sometimes makes this list--but I think he doesn't belong on it--is Winston Churchill
Yes, his famous Zurich speech can be quoted in support of his position as a FF:
Yet all the while there is a remedy which, if it were generally and spontaneously adopted by the great majority of people in many lands, would as by a miracle transform the whole scene and would in a few years make all Europe, or the greater part of it, as free and happy as Switzerland is today. What is this sovereign remedy? It is to recreate the European fabric, or as much of it as we can, and to provide it with a structure under which it can dwell in peace, safety and freedom. We must build a kind of United States of Europe. In this way only will hundreds of millions of toilers be able to regain the simple joys and hopes which make life worth living. The process is simple. All that is needed is the resolve of hundreds of millions of men and women to do right instead of wrong and to gain as their reward blessing instead of cursing.
But Churchill never expected Britain to be a member and remained a nationalist and an imperialist.
See the very useful materials gathered on Jon Danzig's blog page. Danzig, however, take the view--which I don't share--that Churchill would have been in favor of British membership in the EU.