Sessho and Kampaku
In Japan, the Sesshō (摂政) was a title given to a regent who was named to assist an emperor when the emperor was still a child, before the coming of age, or female. The Kampaku (関白) was the title of a regent who assists an adult emperor. The two were collectively known as Sekkan (摂関).
The Sesshō and Kampaku had held the practical powers of the ruling Emperor, conducting cloistered rule until shogunates took over the power from them. Most empresses had Sesshō with some exceptions in the ancient period.
In earlier only members of the imperial family could be appointed to Sessho. Kojiki reported the Emperor Ōjin was assisted by his mother the empress Jingū, but it is doubtful if it is a historical fact. The first historical Sessho was Prince Shōtoku who assisted the empress Suiko.
The Fujiwara clan was the primary holders of the Kampaku and Sesshō titles. More precisely those title was held by the Fujiwara Hokke (Fujiwara north family) and its decendants, to which Fujiwara no Yoshifusa belonged. In 844 Fujiwara no Yoshifusa became Sesshō. He was the first Sesshō who didn't belong to the imperial house. In 876 Fujiwara no Mototsune, the nephew and adopted son of Yoshifusa, was appointed to the newly created office Kampaku. After Fujiwara no Michinaga and Fujiwara no Yorimichi, their decendants held those two office exclusively In 12th century there were five families among the descendants of Yorimichi called Sekke. Until 1868 those five families held those title exclusively with two exceptions of Toyotomi Hideyoshi and his nephew Toyotomi Hidetsugu.
Sekke consisted in five families: Konoe family, Kujō family, Ichijō family, Takatsukasa family and Nijō family. Both Konoe clan and Kujō clan were derived from Fujiwara no Tadamichi, a descendant of Yorimichi. Other three families were derived from one of those two families.
A retired kampaku is called Taikō (太閤), which commonly came to refer to Toyotomi Hideyoshi.
See also List of Sessho and Kampaku