Children are one of the most unique acts of sub-creation that God allows humans to commit. He could create new humans simply by his own will, making them rise fully grown out of dust or rib bone. Instead he makes it a relational act, whereby two human beings decide to create another human being, paralleling his own creation of the first humans. “Let us create man in our image.” Sure enough the children we create are in our own image. It is frightening to think that we have the ability to create a soul of our free will, but God allows us to act like little gods in imitation of our Creator.
Then he gives us the task of raising children, shaping little humans to grow up into big ones. Such is an immense act of creation, like Michaelangelo discovering the Pietà in a block of marble. We get to create beings in our own image and raise them. The command to “Go forth and multiply” is like giving a five year old matches.
Children who enter a family through adoption are no less incredible. After all, adoption is another act of imitating our Father. Every Christian who is not a Jew has been adopted into God’s family. To not be a parent of someone and then to become one; to not be a child of someone and then to become one. Where no connect existed there is now one that is the same being “born by water” as John puts it. Adoption is itself a kind of birth or new birth, with all the wonder of being introduced to a human being you never knew and coming to love them as if things could never have be otherwise.