One theory states that Soga clan was a powerful family that was a native to the area around Kawachi Province by Ishikawa River (present-day Ishikawa River basin in Osaka Prefecture; some even identify the precise location as Ichisuka Kanan-cho, Minamikawachi-gun), or Soga no Sato, Katsuragi Prefecture (present-day Soga-cho, Kashihara City, Nara Prefecture).
河内の石川(現在の大阪府の石川(大阪府)流域、人によっては詳細に南河内郡河南町一須賀あたり)、あるいは葛城県蘇我里（現在の奈良県橿原市曽我町あたり）を本拠にした土着の豪族であった。