This theory is based on the following several facts; first, Munetsuna called himself Hatta; second, in the genealogies of various clans, it is described that his father Soen took the daughter of Masataka MASHIKO, a powerful family in Mashiko, for his wife; third, Munetsuna himself took the daughter of TAIRA no Mikimune, Daijo (the third rank official of Hitachi Province), for his wife; fourth, Tomoie, Munetsuna's second son, also called himself Hatta; fifth, the mother of Asatsuna, Munetsuna's eldest legitimate son, was called Hatta no Tsubone.
これは、宗綱自身が八田を称していたことはもとより、諸氏系図で父・宗円が益子の豪族である益子正隆の娘を室としていることや、宗綱自身が常陸国大掾の平棟幹（大掾棟幹）の娘を室としていること、小田氏始祖となる次男の知家も八田を号されていること、嫡男の朝綱の母が八田局と号されていることなどが背景にある。