The discrepancy resulted from confusion over the date of birth of Sadafuji ISE, who was once thought to be Soun, and from war chronicles written at the beginning of Edo Period, in which Soun was described as having been born in the year of Rat.
これは長年、早雲と思われた伊勢貞藤の生年と混同されてしまった結果であるとし、江戸時代前期成立の軍記物で「子の年」生まれと記載されている。