No, you don't get it. Zoro was 1 when Kaido and Oden fought, and Ushimaru was there. No one left Wano then.
It was clearly explained Zoro is descended from Shimotsuki Kozaburo's people.
It was clearly explained Zoro is descended from Shimotsuki Kozaburo's people.
after oden s death ushimaru resisted 2 more years so he probably sent zoro to east blue with the carpenter