Question: are zoro and ryuma related?
Answer: My though : Zoro might come from sub family of Shimotsuki and may be a descendant of ryuma Shimotsuki or Shimotsuki Kouzaburo. Also he is from Shimotsuki Village. It has been not revealed yet so we can't say it for sure. I wouldn't say he is the descendant of Ryuma but he is definitely related to Wano in some way.