We define love as a tendency in creatures toward union with the good. Love, however has its origin in the eternal. God is eternal love, meaning, that love is an eternal relationship of Father, Son and Holy Spirit. In God the relationship of persons is so close where one lives totally within the other without loss of identity as Father, Son and Holy Spirit. Christ revealed this intimate union when he said, "I am in the Father and the Father is in me". (Jn 14:11) The Father created the universe through his Son and in the Spirit so that creation participates and reflects the love relationship of the Triune God.
Sheen has well expressed the relationship between man and woman in marriage as
a reflection of Trinitarian love thus: "Because
Spirit impregnates marriage, there is first seen in it the reflection of the mystery
of the Trinity. As the Father knows Himself in His Wisdom, or Word, or Son, Who
is distinct but not separate, so the husband discovers opposite to himself one
in flesh with him. As the Father knows Himself in His Son, so man knows himself
through the person opposite. He is present to himself in her for, thanks to sex,
two persons are merged and revealed, one to the other. As the Father and Son are
one in nature through the Spirit of Love that binds them, so the husband and wife
find unity of sex, despite their differences, through the bond of love that makes
them one." (Futon
J. Sheen, Three to Get Married, Society for the Propagation of the Faith,
1951, Ch. 10)
We read in Genesis, "Let us make man in our image, after our likeness. ...God created man in his image; in the divine image he created him; male and female he created them. God blessed them, saying: "Be fertile and multiply ...." (Gn 1:26, 27-28) From this perspective, man and woman are by their union expressing the Trinitarian love of God in giving life to a third, the child. Every child is an incarnation of Spirit because while the parents give of their genetic makeup of the body, the soul is a direct creation of God. So every conception reveals the mystery of God's life, it's a participation in the work of the Trinity.
The parents can conceive and give birth to the child but they cannot pass on God's life to the soul. So, they bring him to be baptized into the body of Christ, the Church. The child is incorporated into the death and resurrection of Christ, and the Trinity begins to dwell in the soul, thus begins a life of faith, hope and love ithrough Christ. Even before the child can speak in silence he or she cries out, God my Father. Now the parents must begin to nurture the faith of the child by example, instruction and prayer, so that the indwelling Trinity may be consciously realized in the life child.