彼は本家の正系として家督を継いだ。
As the legitimate heir of the main family line, he inherited the headship of the house.
この流派の正系を名乗る者が各地に現れた。
People claiming to be the legitimate line of this school appeared in various places.
天皇家の正系をめぐって南北朝の争いが起こった。
The conflict between the Northern and Southern Courts arose over which was the legitimate imperial line.