Original sentence: He was a descendant of the samurai of the (Minamoto) Seiwa Genji line, descended from Emperor Seiwa, that had settled in Ashikaga area of Shimotsuke Province which is in present day Tochigi Prefecture
Edited sentence: He was a descendant of the samurai of the (Minamoto) Seiwa Genji line (meaning he descended from Emperor Seiwa), that had settled in the Ashikaga area of Shimotsuke Province which is in present day Tochigi Prefecture