You are sons of God, so God has given you the Spirit of his Son to form your hearts and make you cry out: Abba, Father.
Because Jesus Christ has appeared, "full of grace and truth," as John says, we have come to know that there is both Lover and Beloved in God. And because the Beloved has joined himself to our humanity in Jesus of Nazareth, we too can become daughters and sons in the Son. Having been joined to the Beloved in Christ, we realize that the Love of the Father remains with us, and this we call the Spirit.
The overflowing Love and Delight that is God is always stretching forth into human hearts and indeed, into all creation. And it is because we have come to enjoy this grace that we realize that there is Lover, Beloved, and Love in God. And these we call the Father, Son, and Holy Spirit.