Many years ago I was babysitting a friend's children. My friend and her family are observant Jews, and I did my best to honor their beliefs and practices. I expected that once each child had gone through their bat or bar mitzvah, and was a responsible adult under the Jewish Law, I would be comfortable respectfully answering questions about the differences between Christianity and Judaism. Until then, I tried to refer such questions to their parents. As often happens, such plans don't always work.
One of the little boys asked me if my God was the same as their God. I answered, "yes." After all, I believe that I worship the God of Abraham, Isaac and Jacob. But the younger brother immediately gasped "No!" He seemed shocked to identify the God of Christianity with the God of Judaism. For these children, raised in a minority faith, maintaining its boundaries, the very separateness (being set apart) of their Jewish identity, was critical. So now the older brother politely asked me what the difference was between Christianity and Judaism. I replied diffidently that Christians believe Jesus was the Son of God.
I was then informed "All boys are sons of God - all Jewish boys, anyway." So it seemed that my statement, which I thought would be shocking to the boys, was simply considered by them to be a matter-of-fact commonplace. Of course, I didn't get into "only-begotten" and the theology of the Incarnation with these children. But I think I learned a lot more from than they did from me. (I should add that I haven't checked this statement with a Rabbi, who might be able to give me a more nuanced explanation of who is and is not considered a Child of God in Judaism. Are Jewish girls considered "daughters of God"? I don't know.) Certainly, in the Hebrew psalms, we can read of the King claiming to be God's son (see Psalm 2).
Flash forward, and there I am reading the Gospel of Luke, which traces Jesus's ancestry all the way back to "Adam, the son of God." In Acts, St. Paul, speaking to the Athenians, refers to them as "offspring of God." In the Epistles in the New Testament, I learn that baptism makes us adopted heirs, or children of God.
So, who are the children of God? I think of it this way: all human beings, descended from Adam, are created children of God - or at least created in order to be children of God. After all, we are all made in God's image, capable of reason, creativity, love. Then, there are baptized Christians, who are children of God by adoption, by the Grace of God in Jesus Christ, and not for any merit of our own. Finally, there is the only-begotten, Incarnate Son of God, Jesus Christ.
It is, of course, perfectly possible that I have this wrong. I know that some Christians do not believe that all humans are children of God. Maybe my ideas are all wrong. But it is refreshing - and challenging - to think that all human beings are, in some sense, my brothers and sisters. Relatives, friends, neighbors, strangers, and enemies - all of us were made in the image of God. This does not mean that baptism is pointless - it binds us to God in a most profound way. For me, it is the very source of my identity. But it is an identiy I claim with humility. How blessed I am to be a created, adopted, beloved, child of God.