The Oki clan is a branch family of the Kamachi clan in Chikugo Province and their ancestor is Masanaga OKI who is a legitimate son of Tomotsuna UTSUNOMIYA, the second son of Kanehisa UTSUNOMIYA of Utsunomiya clan in Chikugo.
大木氏は筑後国の蒲池氏の一族で、筑後宇都宮氏の宇都宮懐久の次男の宇都宮資綱の嫡子大木政長を祖とする。