"when minato 4th hokage was fighting kyuubi his son was born ...after naruto was born his mother died because of blood loss... this is one story.... another is that minato was confused or maybe waiting to use the jutsu (tht devil thing like sword in his mouth) to seal the kyuubi in it ..in tht conclusion he was informed tht he have a son he said to bring him to him ..it is said after narutos mother gave her child to andu so tht he could get him to minato, there was a blast nd she got into it...... (she said to tht anbu when she was giving her child tht "hes the son of 4th hokage dont let a single scratch on him.." } ...thts the story i knw"
Thats true, it apears in the yondaime gaiden, here u have it!!
narushipuden.blogspot.com/2009/08/yondaime-gaiden.html