Rakuin (an illegitimate child) (落胤)
Rakuin is an illegitimate child who is not recognized by his or her father as his child. In particular, rakuin of high class people often comes to an issue. Rakuin is also called as Otoshiin or Otoshigo. They were not recognized as a family of true blood line, therefore they were normally not written in a family pedigree nor appeared in the history.
Though they lived among common people in most cases, they sometimes claimed to be a true heir of authority and were used by powerful people. However, there was no evidence that most of the people on center of the historical stage were real rakuin who had the true blood line (for example Kaigyo TENICHIBO who pretended to be rakuin). Many cases are questioned whether they were true by researchers.
People who were said to be rakuin in the history
FUJIWARA no Fuhito: a Kugyo (high court noble) who lived in Asuka and Nara periods
There is a theory that he was a rakuin of Emperor Tenchi, (which was written clearly in history books and official documents).
Kuya: a Buddhist priest who lived in the middle of Heian period
Although there was a theory that he was a rakuin of Emperor Daigo from his lifetime, it is not clear whether it was the truth or not.
TAIRA no Kiyomori: a busho (Japanese military commander) who lived in the end of Heian period
Although there is a theory that he was a rakuin of Emperor Shirakawa as it was written in "Heike Monogatari" (the Tale of the Heike), it is doubtful whether this is true.
Yoshinao OTOMO: an ancestor of the Otomo clan
There was a theory that he was a rakuin of MINAMOTO no Yoritomo, which is denied now.
Mitsuzumi IWAMATSU: a busho who lived in the middle of Muromachi period. He is said to be a rakuin of Yoshimune NITTA, but it is not clear whether it is the truth or not.
Sojun IKKYU: a distinguished Buddhist priest who lived in the late Muromachi period
He is said to be a rakuin of Emperor Gokomatsu.
Yusai HOSOKAWA: a busho who lived in the Sengoku period (period of warring states)
There is a theory that he was a rakuin of Yoshiharu ASHIKAGA, Seii Taishogun (literally, "great general who subdues the barbarians") of the Muromachi bakufu (Japanese feudal government headed by a shogun).
Shiro AMAKUSA: a person who lived in Edo period
There is a rumor that he was a rakuin of Hideyori TOYOTOMI.
Toshikatsu DOI: a daimyo (Japanese feudal lord), roju (member of shogun's council of elders), and Tairo (chief minister) who lived in Edo period
He was said to be a rakuin of Ieyasu TOKUGAWA in "Tokugawa jikki" (The True Tokugawa Records) and so on.
Heisuke TODO: a member of Shinsengumi masterless warriors' party who lived in the end of Edo period
Although he was said to be a rakuin of the lord of Tsu domain of Ise Province, Takayuki TODO, it is not clear whether it is the truth or not.
The fraud cases sometimes happen in which senior people are cheated out of their money by a man who claimed himself to be a 'rakuin of the imperial family' for example (Arisugawa no Miya fraud and so on).