third son of Imperial Prince Atsumi (son of Emperor Uda

Emperor Uda

was the 59th emperor of Japan, according to the traditional order of succession.Uda's reign spanned the years from 887 through 897.-Name and legacy:Before his ascension to the Chrysanthemum Throne, his personal name was or Chōjiin-tei....

), a kugyo

Kugyo

is the collective term for the very few most powerful men attached to the court of the Emperor of Japan in pre-Meiji eras. The kugyō was broadly divided into two groups: the , comprising the Chancellor of the Realm, the Minister of the Left, and the Minister of the Right; and the , comprising the...

(Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese noble

Nobility

Nobility is a social class which possesses more acknowledged privileges or eminence than members of most other classes in a society, membership therein typically being hereditary. The privileges associated with nobility may constitute substantial advantages over or relative to non-nobles, or may be...

) of the Heian period

Heian period

The is the last division of classical Japanese history, running from 794 to 1185. The period is named after the capital city of Heian-kyō, or modern Kyōto. It is the period in Japanese history when Buddhism, Taoism and other Chinese influences were at their height...

. His mother was a daughter of Fujiwara no Tokihira

Fujiwara no Tokihira

was a Japanese statesman, courtier and politician during the Heian period.-Career:Tokihira was a minister under Emperor Daigo.* 891 : Tokihira was given a rank which was the equivalent of sangi....

. He became Sadaijin

Sadaijin

, most commonly translated as "Minister of the Left", 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 Sadaijin in the context of a central...

 in 978. His daughter Rinshi was married to Fujiwara no Michinaga

Fujiwara no Michinaga

represents the highpoint of the Fujiwara regents' control over the government of Japan.-Early life:He was the fourth or fifth son of Fujiwara no Kaneie by his wife Tokihime, daughter of Fujiwara no Nakamasa...

, when Michinaga was in far lower position. At first he disputed his daughter's marriage because of Michinaga's position, but his wife Bokushi(穆子) pushed the marriage. Finally Michinaga became regent of Emperor, so his wife was a good judge of character. Michinaga came into Masanobu's residence Tsuchimikado-dono (土御門殿).

He is the progenitor of Uda Genji (宇多源氏).

His children were

• Tokinaka (時中) (943–1002) - first son, progenitor of Niwata family and Ayanokōji family
• Sukeyoshi (扶義) (951–998) - fourth son, progenitor of Sasaki family
• Michiyoshi (通義)
• Tomimichi (時通)
• Tokinobu (時叙) - priest (Jakugen, 寂源)
• Naritoki (済時)
• Saijin (済信) (954–1030) - priest
• Rinshi (倫子) (964–1053) - married to Fujiwara no Michinaga
• daughter - mariied to Imperial Prince Munehira (son of Emperor Murakami
  Emperor Murakami
  was the 62nd emperor of Japan, according to the traditional order of succession.Murakami's reign spanned the years from 946 to his death in 967.-Traditional narrative:...
  
  )
• daughter - married to Fujiwara no Sadatoki
• daughter (died 1000) - married to Fujiwara no Michitsuna