
You mentioned that Abraham is the progenitor of the people. I'm taking that you're saying he was just the physical father of the people, in other words, blood relations.
Progenitor also means a person that first indicates a direction, originates something such as a belief, or serves as a model. A person who originates an intellectual movement.
God did start a movement in Abraham. He was directed to leave the idols of his fathers behind and go start a new nation- the "House of Israel"(kingdom of God). These were to be a people who served the one True God by following His commands.
Genesis 17:7 " I will establish My covenant as an everlasting covenant between Me and you and your descendants after you for generations to come."
"I will be your God and you will be My people."
This isn't talking about Abraham's physical descendants. It refers to his spiritual descendants, people who believe in the same God and obey the same commands.
Genesis 18:19 "I have singled him out to command his sons and his household after him to maintain the way of God by just and upright living."
I agree that Jesus was the Son of God as well. "All who are led by the Spirit are sons of God." Abraham had two sons: Ishmael and Isaac. According to man's traditions, Ishmael would have been the inheritor(ruler) of Israel. But Abraham was following God, and according to Him, the inheritance belongs to a person who possesses the Spirit of God, the same Spirit that was in Abraham. This is why Issac was given the inheritance.
"For they are not of Israel which are of Israel. Neither because they are the (physical)seed of Abraham are they all children." The spiritual descendants of Abraham are the children of God.