The royal Roman apples did not fall far from the Patriarchal tree. Their idea of divine kingship derived from the same source as the Jewish one.
Augustus considered himself to be the "Son of God" and his reign to be the fulfillment of prophesy. Shortly after his death it was also declared that he was the product of a "holy birth." So, when these same qualities were claimed for Jesus, it was only in keeping with popular expectations.
The Book of Revelation was written after the literal death of Jesus. It depicts the struggle of his natural line for survival against Roman persecution and predicts the birth of yet another Davidic figure from that line who will prevail over all rivals. Fairly standard procedure for the house of a royal "undergod".
© Charles N. Pope, US Library of Congress. All rights reserved.