In this Pope Francis General Audience, the Pope states that all human persons are children of God, as God is their Creator. But the baptized are children of God by spiritual adoption.
A teaching of the Council of Trent, not mentioned by the Pope in that short Audience, is that those also are children of God by spiritual adoption who receive a baptism of desire:
Trent: “By these words, a description of the justification of the impious is introduced, as being a translation from the state, in which a person is born a child of the first Adam, to the state of grace and of the adoption of the children of God, through the second Adam, Jesus Christ, our Savior. And certainly [this] translation, after the promulgation of the Gospel, is not able to occur without the washing of regeneration or its desire, just as it is written: “unless one has been reborn by water and the Holy Spirit, he is not able to enter into the kingdom of God.” [John 3:5]”
Those who are in the state of grace by any form of baptism — water, desire, blood — receive “the adoption of the children of God, through…Jesus Christ”. And this cannot occur, after the promulgation of the Gospel without baptism by water (the washing of regeneration) or its desire [or a baptism of blood, as we know from other Church teachings]. Before the promulgation of the Gospel, they were saved by a baptism of desire or blood only, and the desire was implicit, as it still can be now.
[1 Corinthians 10]
{10:1} For I do not want you to be ignorant, brothers, that our fathers were all under the cloud, and they all went across the sea.
{10:2} And in Moses, they all were baptized, in the cloud and in the sea.
{10:3} And they all ate of the same spiritual food.
{10:4} And they all drank of the same spiritual drink. And so, they all were drinking of the spiritual rock seeking to obtain them; and that rock was Christ.
And so, even today, many non-Christians have the state of grace by implicit baptism of desire, and so are children of God by spiritual adoption.
Ronald L Conte Jr
the reproach of Christ 
Dear Mr. Conte,
I’ve often pondered the question of when sanctifying grace is infused into the souls of those who have a desire for Baptism. Is it infused when they conceive the desire (whether explicit or implicit)? If so, wouldn’t that render their later sacramental Baptism a mere formality? How would you respond to this question?
Thanks for your time and the work you do for the good of souls.
St. Thomas deals with this question, stating that the adult preparing for baptism, due to his explicit desire for baptism, can receive the baptism of desire. This is less than the formal Sacrament. The Sacrament forgives all sin and all temporal punishment for sin, and gives the indelible character. The baptism of desire forgives all sin and grants the state of grace, but does not take away all temporal punishment nor grant the indelible character. Nevertheless, cooperating fully with grace, which is what is required for a baptism of desire, explicit or implicit, would seem to remove some temporal punishment, just as a good confession does (at least partially).
The Virgin Mary, it is said, received the formal Sacrament of Baptism later in her life, after the Ascension, even though she was sinless and had the state of grace from conception. She received the indelible character, and it is a way of formal entrance into the Church.