Maternal Relative (外戚)
The maternal relative is a family member of the mother or the consort of the emperor or the king.
Summary
In Confucian society that highly regards filial duty, it has been considered that the monarch should take the initiative in according his mother and her relatives every courtesy as an example for the people.
An understanding of 春王正月条, an article written in the first year of Inko (Lu) (B.C. 721) in 'Kuyoden,' which is a commentary of "Shunju" (Spring and Autumn Annals) (i.e., the top article of Shunju), says '子以母貴、母以子貴' (Child is noble for its mother, and mother is noble for her child). Its original meaning was that, if there is no legitimate child and a successor should be selected from among children born out of wedlock, the one born from a mother from the highest ranked origin should be selected. However, the later part of '母以子貴7 was emphasized later, and people understood it as respect for the mother and her relatives. When Emperor Kanmu of Japan raised his maternal grand parents to higher rank posthumously on January 13, 791, he emphasized that his act follows the system of rites by saying '春秋之義。祖以子貴。此則礼經之垂典。帝王之恒範。' in his imperial decree ("Shoku Nihongi" - Chronicles of Japan Continued).
However, his service covered not only financial services, but also social and political authorities, which caused various harmful effects.
China
In China, relatives of the emperor's favorite concubine were raised to high ranks by the emperor to exercise their powers. Especially in a state where a succession race was likely to occur and the emperor favors a specific concubine over others, her relatives were often raised as the guardian of successor candidates under the direct Imperial rule allowing them to have a great political influence.
When a very young emperor ascended the throne, the empress dowager was generally appointed as his guardian, and therefore the empress dowager often raised her own relatives to support herself. An example of this is the tyranny by the relatives of Lu-hou in the early Former Han. In the Later Han, because young emperors continued, the maternal relatives were used as a power to oppose eunuchs, or eunuchs were used to put a brake on the maternal relatives. This often caused political disorder, and the maternal relatives were always the thorn in the side of the dynasty as a poison that monopolizes the powers along with the eunuchs.
On the contrary, the Qin Dynasty performed a reformation of gathering the powers to the king by expelling the maternal relatives who held positions of power, this consequently led to the unification of China by the First Emperor, Shi Huangdi.
Japan
In Japan, the ancient method of making one's own daughter an emperor's bride was practiced, having her give birth to a prince that would be the next emperor, and supporting the prince as his maternal grandfather, thereby increasing and maintaining the political power of his relatives. Using this method, the affairs of state were conducted for a long time by the maternal relatives such as the Miwa clan, the Mononobe clan, the Owari clan, the Katsuragi clan, the Otomo clan, the Fujiwara clan, and the Soga clan. For example, TAIRA no Kiyomori also conducted the affairs of state as a maternal relative.
Korea
In the Korean Peninsula, in the late Yi Dynasty Korea (1392 - 1910) or around the nineteenth century, 'sedo jeongchi' or politics by the Kim clan of Andong district, the maternal relative of the king, was conducted.
Popular maternal relatives
Wang Mang (later emperor of the Xin Dynasty)
Yang Jian (Emperor Wen of the Sui Dynasty)
Huo Guang
Yang Guo-zhong (elder brother of Yang Guifei)
FUJIWARA no Yoshifusa, FUJIWARA no Kaneie, FUJIWARA no Michinaga, FUJIWARA no Yorimichi
TAIRA no Kiyomori