Do not get hung up on the virgin birth, either defending or refuting it. It is an interesting piece of revelation, but it is not essential. Did it really happen this way? I do not know, nor do I really care. God could certainly have done so if it was his wish, but it is not necessary for Jesus to have been her true son. Kinship is about love, not blood or DNA. Our Parent does not need to mate to produce genuine offspring. But that does not mean that this revelation is false or untrue. Learn what there is to learn from it: about God's desire for intimacy with us and our desire to serve our Creator. Just do not wast time trying to prove or disprove it. That's just missing the point.