The true God is indeed the Father of Jesus the Son. I can be brief on this point. For if we know who this Jesus is, we know what a difference that makes; and if we do not, it is not a lecture on theology we need.
Divine offspring, of course, litter the religious landscape. None but the God of Israel has this Son. That means—for a first point—that also in this way the God of Israel is jealous: he will not swap sons with other gods; he identifies himself to himself as the Father of this Son. From and to all eternity, God says to himself: “I am that man’s Father,” and rules all his decisions and acts by that self-identification. Therefore—and this is the second point—literally everything in heaven and earth depends on what sort of person this Son is, and that in the simplest possible sense.
The true God is the Father of the man John Evangelist could call Love Incarnate—and he is nothing but that Father. The true God is the Father of the man Dietrich Bonhoeffer could call The Man for Others—and he is nothing but that Father. The true God is the Father—and nothing but the Father—of the man who raised his friend from from the dead and saved a wedding from fiasco and drove well-meaning merchants from the Temple and begged forgiveness for his executioners and called down judgment on the religious and proclaimed the poor blessed and indeed etc. Would you know who the true God is? Read the Gospels—and that not as teaching about God or his will, but as the story of God, of the Son whose Father he is.
No other God has this Son. Nor would any other want him.
Robert W. Jenson