He is also called the Son of David But we don't call David the father of God.
Mary does not have to be the mother of God, to be the mother of Jesus. She gave him his FLESH. His flesh DIED ON THE CROSS. it was no more. His Spirit (God) Which was before Mary, Before Abraham, Before Noah, Before Adam, Before creation, was risen with a NEW BODY, not bore by Mary. This same body we will get (if we are saved) when we are resurrected! Our old flesh Bore by our mothers) will pass away. Just like the flesh Mary Gave to Jesus did.