Now, if born again Christians are Jesus' brothers and children of God, what are they of the other God, the third supposed person in God, the Holy Spirit? Children, brothers, friends?
People believe in all sorts of things, and every theory has many followers. But it would appear that you are under the wrong impression about the Oneness of God and the different manner He has introduced Himself. Some would and do refer to each as three persons.
All of this comes from leaning on our own understanding, that is, from looking at things from the perspective of being born within this created world. We are like ink spots or animated characters seeing Jesus and thinking, "See, He's created too, only the image of Him, therefore He is not God." But if I said, "The image on the left of your screen is me, and I am also me--I am one"... we all know and understand that both are true according to the identity of me being one. But with God doing the same, we don't understand--though we ought to...BECAUSE HE DREW US A PICTURE for crying out loud, even saying "
I and the Father are One"--just as I have also done. Even so, many do not understand.
But don't be confused by His breaking it down as if speaking to children. Because He is. He first introduced Himself as [One] God, then He introduced Jesus as His Son (meaning "of" Him), and then Jesus in turn in the fulness of time also introduced the Holy Spirit (referring to the spirit of the One who is holy), calling each one by name. And being like children we are expected to understand that Daddy is first known as Daddy; and when we are in public, he is also known as Mister; and when at work he is known rather by his Title. The point being that even in the image of God created in us, a man with children...
is all three: a father, a man, and son.
Still, many do not understand.