The circumstance to the inheritance to a family name of Uesugi clan by Kagetora NAGAO who was a vassal with a different real name was that Norimasa UESUGI always desired to adopt a child to the Uesugi family but was refused from the Satake clan who had adopted a child from the Uesugi family, then made a tough decision to have Kagetora NAGAO, an influential person in Echigo Province, succeed to the family name.
異姓にして家臣筋の長尾景虎が上杉氏の名跡を継承するに至った背景には、かねてから上杉家に養子を招くことを望んでいた上杉憲政が、上杉家から養子を出したことのある佐竹氏からの養子を断られ、苦悩の末に越後国の実力者である長尾景虎に継がせたという経緯がある。