Sons of Abraham?

For a while now, I have been seeing a movement among believers to get back to the roots of the Bible.  They recognize that we have been grafted into Israel spiritually as believers.  Grafting is a common theme that Jesus talks about in the gospels.  John 15:3-5 says it like this, “³ Now ye are clean through the word which I have spoken unto you.⁴ Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.⁵ I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing.”  It is Jesus who we are grafted into.

Ephesians 3:6 says, “That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:” So we who are not Israel, but are believers in Jesus Christ are partakers of the promise.  For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end; (Heb 3:14)  Christ is the promise that was made to Abraham alluded to in Genesis 22:18, And in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice.  It is the blessing that salvation has come to all mankind through the seed of Abraham.
Now, we have to be more specific than that.  There are other nations that can claim to be the seed of Abraham and try to claim the blessing.  Abraham’s first son was named Ishmael.  Normally it is to the firstborn that the rights and blessings are bestowed, but God did not choose Ishmael.  The promise was made to Abraham and Sarah.   Many Muslims today, who are the seed of Abraham through Ishmael, claim this right as the heirs to the promise of God.  But Romans 9:7 says, Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.  So God worked through Isaac and not Ishmael.
http://www.keyway.ca/htm2002/ishmael.htm

But we have to go a step further, for the firstborn and normal heir to the fathers would have Esau, the father of the edomites.  The edomites some say have become in Modern times the Palestinians, and perhaps Saudi Arabia where Wahhabism, a radical form of Islam is practiced and a strong hatred of the Jews is taught. http://www.shalomjerusalem.com/jerusalem/jerusalem83.html
 These people too can claim to be the seed of Abraham, but are not the sons of the promise as the promise went through Jacob. This is reiterated in Romans 9:13 As it is written, Jacob have I loved, but Esau have I hated.  God chose Jacob even in the womb, Rom9:11 (For the children being not yet born, neither having done any good or evil, that the purpose of God according to election might stand, not of works, but of him that calleth;)  And as we know, Jacob became Israel, through whom the promise was passed.
So, to be sure, we can say we are grafted into the seed of Abraham, but saying that is not fully accurate.  We are grafted into Israel, through whom the promises were passed.  This is why it is said that god is the God of Abraham, Isaac, and Jacob.   In exodus 3:6, God identifies Himself that way, Moreover he said, I am the God of thy father, the God of Abraham, the God of Isaac, and the God of Jacob. And Moses hid his face; for he was afraid to look upon God. 
These are important distinctions to make, the clarification significant.  Understanding these differences can open a door to understanding what is going on in the middle east today.  This is why Jerusalem and Israel are such stumbling blocks to the world.  Each of these sons of Abraham all lay claim to the promised land.  Understanding the relationships between these other sons of Abraham to the sons of promise, Isaac and Jacob will also help you to understand what is to come.  The key to prophecy is tied in to these relationships, and the key to truth is understanding through whom the promises were established.  It is in Jesus Christ that we are grafted in, the promise of God through Abraham, Isaac, and Jacob (Israel), not through any other.