You are getting all knotted up in the various characters that went into the composite of the mythical Jesus. There was Judas the Galilean who was probably born in 14 BC - possibly on 6 January. He was the main Jewish Jesus. But there were other Jewish "messiah" types scattered along the years up to the Bar Kochba rebellion when Simon bar Kockhba - "the son of the star" - (
http://en.wikipedia.org/wiki/Simon_bar_Kokhba) rebelled against Rome in the 130s. A close and careful reading of Josephus will reveal that many of the incidents portrayed in the gospels and Jesus legends were derived from the activities of some of these. In fact, incidents from the gospels and Acts of the Apostles were adapted from Josephus' own autobiography! I've even found incidents in Tacitus and Dio Cassius that went into the writing of the gospels.
So, you have a mishmash of Jewish messiahs formed into a composite and overlaid on the truly redeeming life of Julius Caesar who, because of his extraordinary qualities, and the love the people had for him, was deified - thus giving the model of a man who became a god at his death.
In the earliest gospel, "Jesus" only became the son of god upon his resurrection (ascension). In the next stage, he became the son of god upon his baptism in the Jordan; next stage: he was born the son of god (a god and human woman) in the style of the ancient Greek gods. So, there were a number of combined elements and stages of development. You might enjoy reading "The Incredible Shrinking Son of Man" by Robert M. Price for some fun exposition on these factors. Though, of course, Price suffers from the defect of not having thought of Caesar being there in the mix.