Saigo Siro

Saigo was the extramarital birth son of Saigo Tanomo (1830-1905), lord of the Aizu samurai clan of Japan and master of the Daito-Ryu aikijujutsu martial art, hereditary in the clan. In 1885 Saigo senior was erroneously reported to his family to have been killed (sources differ: either in battle or executed for rebellion by the Meiji government), and according to custom, the entire family - wife, children and others, at least 14 people in all - committed ritual suicide in shame.

This left Saigo senior with no legitimate eldest son to pass the secrets and mastery of Daito-Ryo to on his death, so he legitimized Siro by formal adoption in 1887 and taught him everything. Unfortunately Siro fell in love with the daughter of Jigoro Kano, master of Kodokam judo and defected to that system. Saigo senior then chose Masayoshi Sokaku Minamoto Takeda (the nephew of his predecessor, Soemon) as his successor, while Siro eventually left Kodokam judo as well.

References

Cunningham, Steven R. "A Brief Look at the 'Root Arts' of Judo." Formerly available at: http://www.bethwood.com/cunningham/ju01002.htm
"Interview with Takeda Tokimune: Part 4," in: Daito-ryu Aikijujutsu: Conversations with Daito-ryu Masters, edited by Sanley A. Pranin. (Aiki News, 1995). Also available at: http://www.daito-ryu.org/tota4.html
"Daito-Ryu." Available at: http://www.geocities.com/Tokyo/1235/history.html
Yamaguchi, Shihan. "Break-Away Students." Available at: http://www.geocities.com/Tokyo/1235/articles.html