In seeking to understand the traditional family, Christians should keep in mind that not only are individual persons created in the image of God, but so is the family itself. The human family is the closest analogy that mankind will ever come to concretely understanding the Blessed Trinity.
The creeds teach that while there is one God, He exists in three distinct persons. The bible, on the other hand, reveals that man is made in the 'image of God'. From these two truths, therefore, we can acknowledge that the complete image of God is found in the Triune understanding of Him.
This understanding of His Triune nature is reflected by the human family whose personal relationships approach the likeness of the Trinity. There are multiple demonstrations of this truth.
Consider the unity of the Trinity which is reflected in the unity of the family. Or the "family of persons" which is found in both. The persons of the Trinity share the 'same substance ' while a human family becomes one flesh: wife with husband and parents with children.
There is also another element in the Trinity that lends itself to human likeness. The Nicene Creed professes this about the Trinity: "We believe in the Holy Spirit, the Lord, the giver of life who proceeds from the Father and the Son."
In Catholic theology, the Holy Spirit is said to proceed from the will of both the Father and the Son, or in other words, through the activity which they engage in, otherwise known as "love".
The Holy Spirit is poured forth through the exchange of love between the Father and the Son. This is why perhaps Jesus says to the Apostles: " Unless I go away, the Counselor will not come to you; but if I go, I will send him to you." (John 16:7)
In the eternal economy of the Trinity, therefore, a person 'proceeds' from the love between two other persons. And so, the Holy Spirit is love 'proceeding' or 'coming from' the first two persons of the Blessed Trinity.
The human family has a rather striking parallel to this dynamic. The ultimate act of intimacy in a marriage mirrors the eternal exchange of love between the first two persons of the Trinity.
And like the eternal or continual procession of the Holy Spirit in the Trinity, the act of love between a man and a woman causes a 'procession' of another human person (i.e. the birth of a child).
Thus, it is precisely because the homosexual sex act is not ordered to the procession of another person, that it can never be a Trinitarian reflection of the divine essence.
Indeed, the sexual act itself, which is supposed to be a reflection of the Trinitarian relationship, becomes, through the homosexual act, a blasphemy against God since it ends up distorting the Trinitarian image of Him.
The human sexual act either affirms God's image or it distorts it. This is why all forms of contraceptive sex, including the homosexual act, are serious sins: they seek to create God in another image. It is anti-Trinitarian.
http://catholic-legate.com/articles/antitrinity.html
