According to Catholicism, why is the Holy Spirit never spoken of as the Father of Jesus? The sixth article of the creed recites:


  He was conceived by the power of the Holy Spirit and born of the
  Virgin Mary.


Now a woman conceives by the agency of a man who becomes the father of that child.

What is the Catholic theological explanation as to why the Holy Spirit is never spoken of as the Father of Jesus? In Catholicism it is always understood that God the Father is and always is the Father of Jesus.

Moreover, one of Mary's title within the Catholic Church is Spouse of the Holy Spirit. [cf. Enyciclical Redemptoris Mater, 26 | Pope St. John Paul II].

Please note the two natures in Jesus, the nature of God and the nature of man. This question is more interested in his nature as man.

To make things complicated, Joseph is referred to as the father of Jesus and Jesus as the Son of David.

Asking another way,  why isn't the title "father" even remotely applied to the Holy Spirit when it is by his power that Jesus, God the Son made man was conceived in Mary?
Jesus had two fathers. One was Joseph, his earthly adoptive father. The other is the Father, his heavenly father (and ours as well). He had no earthly biological father.

That is the distinction. The Father is not Jesus' earthly father in any sense whatsoever. The person of Christ is eternally begotten of the person of the Father. That doesn't and didn't change when he became a man, but it doesn't mean he was temporally or humanly begotten by the Father. A father is a father of a person, not of that person's nature.

But of course, "When [Jesus] came into the world, he said, 'Sacrifice and offering you did not desire, but a body you prepared for me.'" In what sense did the Father "prepare" a body for Jesus? Was it in his capacity as a father? No. His "fatherhood" is not in view at all in Hebrews 10, nor in Psalm 40, which is being referenced. Haydock paraphrases the verse by saying, "Thou didst decree I should be made man." What's in view is God's decree, not his begetting. Haydock emphasizes that Hebrews is speaking of Jesus' willingly becoming man, which Pope Benedict XVI agrees with in this homily: "In this double yes the obedience of the Son is embodied, and Mary gives him that body." I'm sure Jesus prayed with the psalmist, "You knit me in my mother's womb," but that's because that's what God does for all men, not because he begat him.

Mary conceived Christ by the power of the Holy Spirit, but this was miraculous, virginal, nonsexual, and nonmarital. On one website, I found an argument that she had to be wed to the Holy Spirit or else the conception was fornication -- but fornication requires sex! There was no sex, that was the whole point of calling it "miraculous." So the Father is not Jesus' father in the same sense that we have fathers, and neither is the Spirit.

Rather, the "Spouse of the Holy Spirit" title is metaphorical, as Pope Paul VI indicated in Marialis Cultus: "Examining more deeply still the mystery of the Incarnation, [the church fathers] saw in the mysterious relationship between the Spirit and Mary an aspect redolent [i.e. suggestive] of marriage, poetically portrayed by Prudentius: 'The unwed Virgin espoused [i.e. married] the Spirit.'"

Could the Holy Spirit be called Jesus' father in a metaphorical sense? I don't see why not -- in theory -- other than that it hasn't happened yet. It also could be confusing, since obviously Jesus' father is the Father, and the doctrine of the trinity is confusing enough without two of its persons having the same title (albeit in different senses). So will it happen in reality? It seems doubtful.