Genshin UDAGAWA who was Yoan's adopted father, Genzui UDAGAWA who was Genshin's adopted father, and Kosai UDAGAWA who was Yoan's adopted son are known as a Rangakusha and a scholar of Western Studies.
養父である宇田川玄真、またその養父である宇田川玄随、養子である宇田川興斎も蘭学者、洋学者として知られている。