The Nature of our Supernatural Adoption by God
The first man, Adam, as scripture says, became a living soul; but the last Adam has become a life-giving spirit. That is, first the one with the soul, not the spirit, and after that, the one with the spirit. The first man, being from the earth, is earthly by nature; the second man is from heaven. As this earthly man was, so are we on earth; and as the heavenly man is, so are we in heaven. And we, who have been modelled on the earthly man, will be modelled on the heavenly man.

1 Cor. 15:45-49

"By the mystery of this water and wine may we come to share in the divinity of Christ, who humbled himself to share in our humanity."

The Mass

"My main point in teaching was to make my students realize what Christianity is -- that it's not just being good with the grace of God helping us, but it means real transformation, that you are sharing the divine nature. This must be taken seriously."

Godfrey Diekmann, OSB

Writer's position on this Issue -

A Christian is a person who has been given a Share in the Divinity of Jesus Christ and whose nature is no longer solely Human but is now, like Jesus and through Jesus, God/Human.

Only three people have been BORN with the nature of God/Human. Jesus and His Mother Mary, both of whom were also CONCEIVED as God/Human (but not in the same way), and Jesus' cousin John, who was not conceived as God/Human but who ACQUIRED the nature of God/Human while in his mother, Elizabeth's, womb when she had a visit from Mary when she was expecting Jesus.

Jesus was conceived as God/Human in the manner of Himself as God creating and taking upon Himself the new nature of God/Human. His Mother Mary was conceived as God/Human in the manner of (the most appropriate) one of us receiving a Share in the Divinity of her Son, Jesus Christ. She is the Perfect Christian.

Every one of us can also ACQUIRE the nature of God/Human by "freely choosing" to accept our Share in the Divinity of Jesus Christ through the method given to us by Him, Baptism.

It is strongly recommended that you read the Article about Supernatural Adoption in the OnLine Catholic Encyclopaedia.

In particular, I would draw your attention to two passages which I now quote here.

Firstly,

The charter of our adoption is properly recorded by St. Paul (Romans 8; Ephesians 1; Galatians 4); St. John (Prologue and I Epistle 1, 3); St. Peter (I Epistle 1); and St. James (I Epistle 1). According to these several passages we are begotten, born of God. He is our Father, but in such wise that we may call ourselves, and truly are, His children, the members of His family, brothers of Jesus Christ with whom we partake of the Divine Nature and claim a share in the heavenly heritage. This divine filiation, together with the right of co-heritage, finds its source in God's own will and graceful condescension.

and secondly,

In spite of all the catechetic and polemic uses to which the Fathers put this dogma, they left it in no clearer light than did their predecessors, the inspired writers of the distant past. The patristic sayings, like those of Holy Scripture, afford precious data for the framing of a theory, but that theory itself is the work of later ages.

I would also draw your attention to the following passage from Chapter 3 - "Sharing Divine Life" - of Clifford Howell's book -

If the notion of sanctifying grace as the supernatural life of the soul is now clear, we are in a position to understand another idea which is part and parcel of that "mature Catholicism" described in the previous chapter. This is the idea of the "Mystical Body of Christ". We must understand that it is only through the Mystical Body that we acquire our personal share in the divine life; and that it is within the Mystical Body that our personal activities in the supernatural order can come to fruition.

You will frequently find expressions in Catholic literature such as those above - "partake of the Divine Nature", "share in the divine life" - but you are less likely to come across the more extreme and definite-sounding "Personal Share in the Divinity of Jesus Christ, the Incarnate Son of God". Subject to any future Dogmatic Interpretation by the Catholic Church, that is this writer's position on the Nature of our Supernatural Adoption. This is primarily because, in trying to describe an unfragmented coherent Model of what God's relationship with Us is all about, it is the only interpretation which both holds it all together and eliminates vagueness.
It is also strongly recommended that you read the following two Articles from FINDarticles.com -

'Christian, remember your baptism'. (1997 address from Fr. Godfrey Diekmann)
Diekmann says hold fast to hope. (Vatican II figure Godfrey Diekmann)

and the following Encyclical Letter of Pope Pius XII -

MYSTICI CORPORIS CHRISTI

It seems extraordinary that a Dogmatic definition of such a pivotal issue remains outstanding.