, also known as Go-Ono no Miya (後小野宮), was fourth son of Fujiwara no Tadatoshi. He became udaijin

Udaijin

Udaijin , most commonly translated as the "Minister of the Right", was a government position in Japan in the late Nara and Heian periods. The position was consolidated in the Taihō Code of 702. The Asuka Kiyomihara Code of 689 marks the initial appearance of the Udaijin in the context of a central...

(Minister of the Right) in 1021, and lived to be ninety. He became adopted heir of his grandfather Saneyori

Fujiwara no Saneyori

, also known as Onomiya-dono, was a Japanese statesman, courtier and politician during the Heian period.-Career:He was a minister during the reigns of Emperor Reizei and Emperor En'yu....

, the head of Ononomiya family (小野宮家), and he inherited vast estate and documents of Ononomiya family. Sanesuke had a thorough knowledge of customs and rites, so he was called Kenjin Ufu (賢人右府) (wise Udaijin). He wrote the diary Shōyūki (小右記) for fifty years.

Sanesuke is mentioned in the Diary

The Murasaki Shikibu Diary

The Diary of Lady Murasaki records the daily life of the Heian era lady-in-waiting and writer, Lady Murasaki Shikibu, author of The Tale of Genji...

 of Murasaki Shikibu

Murasaki Shikibu

Murasaki Shikibu was a Japanese novelist, poet and lady-in-waiting at the Imperial court during the Heian period. She is best known as the author of The Tale of Genji, written in Japanese between about 1000 and 1012...

, author of Genji Monogatari. In it, she praises him for being out of the ordinary, and describes in detail a number of occasions of his superstitious behavior. In the Diary, Sanesuke is described as having summoned exorcists on a number of occasions, and employed children in the beating of gongs to cure him of illness or nightmares.

He was married to a daughter of Minamoto no Koremasa (descendant of Emperor Montoku

Emperor Montoku

was the 55th emperor of Japan, according to the traditional order of succession.The years of Montoku's spanned the years from 850 through 858.-Traditional narrative:...

), and also married to Princess Enshi (婉子女王), daughter of Imperial Prince Tamehira. She was a consort of Emperor Kazan

Emperor Kazan

was the 65th emperor of Japan, according to the traditional order of succession.Kazan's reign spanned the years from 984 through 986.-Traditional narrative:...

 and married to Sanesuke after Emperor became a priest. From these two marriages he couldn't have any child. He adopted nephews. He had two biologic children from maids in his late life.

• Ryōen (良円) - priest
• Chifuru (千古) (daughter) - married to Fujiwara no Kaneyori (son of Fujiwara no Yorimune)

Two adopted children are the sons of Fujiwara no Kanehira. Kanehira was Sanesuke's elder brother.

• (adopted son) Sukehira (資平) (986–1068) - heir of Ononomiya family
• (adopted son) Sukeyori (資頼)