5 God then is in an improper sense the Father of many, but by nature and in truth of One only, the Only-begotten Son, our Lord Jesus Christ; not having attained in course of time to being a Father, but being ever the Father of the Only-begotten. Not that being without a Son before, He has since by change of purpose become a Father: but before every substance and every intelligence, before times and all ages, God has the dignity of Father, magnifying Himself in this more than in His other dignities; and having become a Father, not by passion, or union, not in ignorance, not by effluence, not by diminution, not by alteration, for every good gift and every perfect gift is from above, coming down from the Father of lights, with whom can be no variation, neither shadow of turning. Perfect Father, He begot a perfect Son, and delivered all things to Him who is begotten: (for all things, He says, are delivered unto Me of My Father:) and is honoured by the Only-begotten: for, I honour My Father, says the Son; and again, Even as I have kept My Father's commandments, and abide in His love. Therefore we also say like the Apostle, Blessed be the God and Father of our Lord Jesus Christ, the Father of mercies, and God of all consolation: and, We bow our knees unto the Father from whom all fatherhood in heaven and on earth is named: glorifying Him with the Only-begotten: for he that denies the Father, denies the Son also: and again, He that confesses the Son, has the Father also; knowing that Jesus Christ is Lord to the glory of God the Father.
Source: Catechetical Lectures (New Advent)