And who was it that made Eve?
In any case, if we allow Eve as a "child of God" then that doubles the original number, but still remains only 2. We, you and I, are not children of God by virtue of our existence, rather, we are "sons of man" (as Jesus called himself) and we are sons of the Devil, as he also described us.
We are not all God's children, as so many assert, mostly those who try to rationalize there abberant behavior by asserting "God made me this way", which is rubbish. God does not cause anyone to sin, James 1:13-15.