The Ishikawa Clan (石川氏)
The Ishikawa clan was a family that assumed the family name of Ishikawa.
There were three main branches of the Ishikawa clan.
A branch of the Soga clan or Soga no kura no yamada no ishikawa no maro line Ishikawa clan.
The Ishikawa clan (of Seiwa-Genji)
The (MINAMOTO no Yoshitoki line) Ishikawa clan
This was one of the branches of the Ishikawa clan, whose ancestor was MINAMOTO no Yoshitoki, the sixth son of MINAMOTO no Yoshiie (Hachimantaro Yoshiie). To prevent confusion with other clans, it was instead called Ishikawa-Genji (Minamoto clan).
In the Genpei War, the clan lost many members because it was smashed by the attack of MINAMOTO no Suesada, who belonged to the Taira family despite assuming the name of the same Minamoto clan. However, after the victory of the Minamoto clan over the Taira family, it resumed its sway and expanded its power to the Southern area of Kawachi Province (Kawachinagano City, Osaka Prefecture).
In the Kamakura period, it became a major force. However, as the Kamakura bakufu (Japanese feudal government headed by a shogun) fell into a decline and the local powerful clans, such as the Iyotachibana clan (the Ochi clan) represented by Masashige KUSUNOKI, emerged in the Southern area of Kawachi Province, it began to lose its power, being overwhelmed by such new forces. As a result, many of the members of the clan dispersed over the country, leaving their native land. However, there were also a quite a few members who remained in Kawachi under the control of Masashige KUSUNOKI.
It is considered that the Nakagawa clan (represented by Kiyohide NAKAGAWA) in Settsu Province, which became eminent in the Sengoku period (period of warring states), had traced its lineage to this Ishikawa clan (There is also another theory that it descended from Tada-Genji (Minamoto clan), which was related to the family).
The Mikawa-Ishikawa clan
There was the Ishikawa clan in Mikawa Province, from which Kazumasa ISHIKAWA came to the forefront in the late Sengoku period. It is said that the origin of the family was from Yoshitoki's descendants, which had once relied on the Oyama clan in Shimotsuke Province and later settled in Mikawa following Rennyo (head-priest of the Jodo Shinshu sect [the True Pure Land Sect of Buddhism]). The clan served the Matsudaira family (the Tokugawa family) as Hitto karo (the head of chief retainers) for generations. It is said to have been one of the seven Anjo fudai families (a fudai daimyo who had been serving Ieyasu since he was in Anjo), which were the oldest among Tokugawa families, and appeared in Ryueihikan (a book describing events, regulations or standards, etc. of the Edo bakufu). It is also said to have been the representative of the adherents of the Jodo Shinshu sect (believers of the Jodo Shinshu sect) in Mikawa Province.
The aforementioned Kazumasa had been actively involved in serving Ieyasu TOKUGAWA until he ran away to Hideyoshi TOYOTOMI. After that, he served Hideyoshi as his vassal and later became daimyo (Japanese feudal lord). However, his descendants were treated coldly by Ieyasu, who had established the Edo bakufu after Hideyoshi's death, and shortly after that, they were punished by being deprived of their fief. The branch of the Ishikawa family which thrived as fudai daimyo (a daimyo in hereditary vassal to the Tokugawa family) in the Edo period had been derived from the lineage of Ienari ISHIKAWA, who was an uncle of Kazumasa.