家か系けい伝でん説せつ

noun

family legend

A traditional story or myth about the origins, history, or notable events of a particular family or lineage.

• 彼かれの家いえには、先せん祖ぞが侍さむらいだったという家か系けい伝でん説せつがある。

  His family has a legend that their ancestors were samurai.