United Nations: The First Fifty Years By Stanley Meisler said:At the request of Roosevelt, who was hoping to fashion a new Latin American champion just like China in Asia, Stettinius suggested that Brazil join the Security Council as the Sixth Policeman. But Cadogan and Gromyko objected, and the matter was dropped. Roosevelt, however, told Stettinius that Brazil was still a card up his sleeve.
At Dumbarton Oaks, Roosevelt was setting up Brazil to be a world power to help police the world, and had his Secretary of State suggest them to be a permanent Security Council member of the United Nations. The Brits and Soviets were against it, and that was that. The book also mentions that Churchill rejected the idea that China could be a world power, and FDR did not like the inclusion of France because he disliked De Gaulle (though he did think they were capable), and other squabbles like the Soviets trying to get each of its component republics to join as a separate GA member.
But what if FDR had been able to convince the others that Latin America needed representation?
'Brazil Seeking Security' by Stewart Patrick said:Brazil’s candidacy has been a bone of contention since World War II, when the Big Three debated who should join them as veto-wielding permanent members. Churchill ultimately won agreement on liberated France, which Stalin had dismissed as “charming but weak.” Roosevelt secured support for Chiang Kai-shek’s China, on the grounds that they needed at least one Asian member.
Roosevelt also lobbied hard for Brazil. Beyond rewarding the country’s participation in the war, he was impressed by its massive size, resources and potential. He worried that a council without a permanent Latin American member would undermine hemispheric solidarity, and that a dissatisfied Brazil might quit the UN altogether—just as it had left the League of Nations when denied a seat on the League Council.
Other U.S. officials were skeptical. Brazil was in no way a great power, and treating it as one would undermine the council’s credibility. Moreover, Brazil’s selection would antagonize its Spanish-speaking neighbors, while emboldening other regional powers to make similar claims. Despite Roosevelt’s support, Brazil’s bid was ultimately thwarted by London and Moscow.
Brazil was one of those johnny-come-lately declare war at the very end entrants into WWII, but what if they had joined up earlier? True, military participation would be limited at best, but what if they had been a greater participant diplomatically and economically speaking for the Allies? This goes beyond getting a permanent seat at the U.N. - it's also what if they were taken seriously earlier as a regional power, and in general if there were greater Latin American participation in the organization. I guess having an even-number of seats in the U.N. doesn't matter, since vetoes make ties a moot point anyway.