It is said that KOMA no Jakko (and his family), who had been serving as a local magistrate of Koma County since the county's formation in 715, was Fukushin's family member and Fukushin himself had a powerful influence over the province.
なお、福信は霊亀元年（715年）の高麗郡設置以来、同郡の郡司であった高麗若光（およびその一族）と同族と考えられており、福信自身も同国内に大きな影響力を持っていたとみられている。