It's been pretty clear since the first SBS that talked about the ship from Wano that Zoro had an ancestor (grandparent based on the time)
D: In Ch. 909, was the carpenter boss that appeared in Wano the same one that was introduced in the Volume 7 SBS, Minatoma-san? P.N. Yacchi
O: Yes he is!! Back then, he was fixing the broken door to the bar in Foosha Village. He was introduced as Carpenter Minatomo-san, exclaiming "Who did this!?". And now, he somehow ended up in the New World in the closed bordered country of Wano! Isn't that weird!? That's right, they actually aren't the same person! They have the same last name because they're related by blood. The fact of the matter is, a ship from Wano reached East Blue a few decades ago.
One of the descendants of someone on that ship is a person that everybody is familiar with...
This part might be featured later in the main story so I won't mention any more than that. It isn't going to be a major plot line, it will just be a minor story.
"A character that everyone is familiar with" could only ever be Zoro, not his master who's barely had a role in the series. And Oda's said it's not going to be a big deal.
Given that Zoro's given name is Roronoa and not Shimotsuki chances are it was either a grandmother on the ship who married into someone from the village, or they had a daughter.