My father, Yukio Maetoku, was born in Okinawa in 1936. He later moved to Argentina after WWII. He said to us that his grandparents were either Argentineans or lived in Argentina for a long time. His mom, Fusako Yamashiro, was born in Hawaii and later moved to Okinawa where she married Hideo Maetoku. They had 3 children and they both died during WWII. So... if we're talking about the same families, your greatgrandparents moved from Argentina to Hawaii and then back to Okinawa. But I don't have much more information to confirm all this. I believe that my father's grandparents were Koki and Uto Yamashiro. Do you know your great grandparents' names?