5 No longer will you be called Abram; your name will be Abraham, for I have made you a father of many nations. 6 I will make you very fruitful; I will make nations of you, and kings will come from you.According to Wilson (see reference in previous posts), pg 20, this word "nations" is "goyim", or "Gentiles".
In other words, from the very beginning of the Abrahamic covenant, God promised that Gentiles would be part of the Abrahamic family.
To any Jew who might be reading this, I am your brother, and you are mine, not because all Goyim are brothers to the sons of Abraham, but because those Gentiles who are part of the new covenant (which is unlike the Mosaic covenant - Jer. 31:31ff) are brothers to the sons of Abraham.