In Ephesians 5:29, Paul says that nobody ever hated their own flesh but nourishes it and cherishes it. Then he states that the Lord does so also to the church. Then Paul states that 'we are of his body, of his flesh and of his bones'.
Then Paul quotes Adam's words (which are re-iterated by Jesus of Nazareth) :
For this cause shall a man leave his father and mother, and shall be joined unto his wife, and they two shall be one flesh [Ephesians 5:32 KJV]
But he makes it clear that he is still speaking of Christ and the church within this context and he says that it is a great mystery of which he speaks.
The headship of Christ over the church is clearly the reason that male and female were created in the beginning. God has expressed, in his creation, that which expresses himself and his own purposes in making a creation at all. The ultimate reason is that there might be one body, a bride, as seen in the visions of the Revelation of Jesus Christ.
But the headship regarding man and woman is not associated, in Paul's argument, with the relationship of Christ and God. In Paul's argument (and I am here quoting Paul as being a 'Trinitarian theologian') Christ and the Church is the way to see the headship regarding man and woman. These are what are compared.
The Son of God, come in humanity, is the Christ.
The Christ is the head of the church. And, in humanity, he who descended (from heaven, to partake of humanity) is now, in humanity, raised and ascended, to be the Head over one body.
Raised in humanity, he is also seated at the right hand of Deity. What does 'God' mean ? is asked and the answer is that the Greek word Theos may be translated 'Deity' for it is not a name, nor a title - it is a concept.
The relationship of Deity to the One, eternally the Son of God, now raised in humanity is that Deity, as such, as a concept, has headship over the humanity that now is seated at the right hand of God.
But the relationship of Father and Son is another thing altogether and must be considered separately. That is to say, it is another question.