Musashibō Benkei (武蔵坊弁慶) (role )Oniwakamaru (鬼若丸)
"The son of a bonze of the Kumano temple (Kii). In his infancy he was called Oniwaka-maru 鬼若丸; having become a bonze, he took the name of Musashi-bō. Contrary to his calling, he always evinced a greater taste for fencing and other military exercises than for the cenobite life. One day on the Gojō bridge (Kyōto), he attacked Minamoto Yoshitsune, then quite young. Having been overpowered by the young lord, he became his faithful follower. He accompanied him in his expedition against the Taira, and afterwards in his flight in Ōshū to the residence of Fujiwara Hidehira, and finally died with him at the battle of Koromo-gawa after wonderful deeds of valor (1189). Legendary accounts have embellished Benkei's adventures and popularized his strength, stratagems, and devotedness to Yoshitsune. It went so far as to suppose him to have escaped the disaster at Koromogawa, and to have fled into Ezo with his master."
Quoted from: Historical and Geographical Dictionary of Japan by E. Papinot, p. 45.
In 1910 James de Benneville published Saitō Mussashi-bō Benkei : (Tales of the wars of the Gempei) Being the story of the lives and adventures of Iyo-no-Kami Minamoto-Kurō Yoshitsune and Saitō Musashi-bō Benkei the warrior monk. In the introduction to this volume de Benneville said: "A man cannot be born of two mothers..." Interesting since more than one woman is said to have been the mother of Benkei.
"Benkei's father is sometimes assumed to have been a mountain-god or yamabushi, but in a more historical context especially Benshō or Benshin, a highly-placed Buddhist functionary of the Kumano temples is mentioned. In this connection - according to other sources — Benshō is also known as the seducer of a Fujiwara lady on a pilgrimage to the Kumano-tokoyo. Thus Benshō was the father of her onigo. The child has to be killed, but the mother manages to have it taken to the mountains to be raised under the significant name of Wakaichi. In other traditions Ita gozen is mentioned as Benkei's mother. Her grave is supposed to be located near Chizu..."
Quoted from: Namazu-e and Their Themes: An Interpretative Approach to Some Aspects of Japanese Folk Religion by Cornells Ouwehand, p. 174.
De Benneville tells us that Benkei's mother, a peasant woman named O'Haya, had shunned all suitors. She had quite a few of them because she was very attractive, but she was also stronger than the men that wanted her and strong enough to fend off their testosterone driven lust. This frustrated O'Haya's father who wanted an heir to his line, albeit a peasant one. Finally O'Haya agreed and went off to a shrine to the Kannon to pray for a male heir. "I will go and pray to Kwannon-sama at the Kami-no-kura temple at Mi-Huzue. She will tell me how to get a child." Everytime O'Haya went to seek help she had to pass by the fierce, oversized Ni-o or guardian figures. She also had to give a small donation to the temple. As time passed her purse grew thinner and so did she.
On one of her visit, weak from hunger and almost hallucinating, O'Haya was confronted a "huge figure of a scarlet hue" which forced her to swallow a large bolus. After that she could remember nothing of what happened. She didn't even know how she ever got back home, but her father found her weak and faint just outside their modest hovel. Soon O'Haya began to show signs of her pregnancy, but after 9 months the baby was still not born. Her father began to wonder if his daughter's condition wasn't due to a tumor instead. Two years passed. No baby. Three years. Still no baby. Then after three years, three month she gave birth to an extraordinary baby boy with a full set of teeth, long hair and who could run like the wind. Because the baby was born on the third day of the third month, Buddha's birthday, he was named Shinbutsu-maru.
Of course, there is another background story as to who or what had fathered this child. De Benneville pointed out that the true father most likely Benshō, the all to human, monastic guardian of the temple. O'Haya had gone along with the story of Ni-o as a cover up. Besides, if Benshō had taken credit for all of the children he had fathered through woman who came to pray to the Kwannon then he and that temple would have been financially strapped in the least and broken at most. But, of course, that does not explain the three plus years of pregnancy, the long hair, the teeth and other wondrous accounts of Benkei's birth.