the same passage mentions that Mary asked how she could become pregnant when she was a virgin, and the angel says that "nothing is impossible with God." God can do anything, for Him to create a person without a father, or even without a mother, as was the case with Adam, is no problem. Therefore, it is quite absurd to make the conclusion that Jesus must be a literally begotten son of God simply because he doesn't have a father.
In any event, Christians have themselves disagreed as to what being a begotten son of God actually implies. I mean, they all believe God Himself didn't actually impregnate Mary physically. They say, God sent the Holy Spirit which entered into Mary and miraculously caused her to become pregnant. They also believe that on the Day of Pentecost, God sent the Holy Spirit which entered into the disciples and they miraculously began to speak in foreign tongues.