The stories say that Benkei stayed in the womb of his mother for 18 months (or three years according to "Benkei Monogatari"), and when he was born, he was already as large as a two- or three-year-old boy with his hair long down to the shoulders and all back teeth and front teeth fully grown.
母の胎内に18ヶ月（『弁慶物語』では3年）いて、生まれたときには2、3歳児の体つきで、髪は肩を隠すほど伸び、奥歯も前歯も生えそろっていたという。