Reading through Romans 9 my attention is drawn to the discussion about who are the true people of Israel. In our lives today this might not seem like a major discussion point, yet in the days of Jesus, and even in the Middle East now, the topic of who is a true child of God is a really big issue. The classic measure in the Jewish world is your ancestral connection to Abraham. From the blood line of Abraham comes all the people of God. Paul who can trace his heritage all the way back to Abraham challenges the qualification.
Paul offers that it is not through our ancestry we are connected to God, rather it is through the promise of God. Abraham was given a promise, and that promise was to be the father of a great nation. When the promise was delivered to Abraham he was childless, and the prospects of having a child were not real high. So how is it that Abraham would be the father of a great nation? Not through natural birth, rather by spiritual birth. All those who would follow after the promise of God would be a part of the people of God.
Before the Christ engaged his earthly pilgrimage the way you were identified as being a part of the promise was to be connected to the family of God through a bloodline. Once Christ journeyed to earth, lived, died and rose, the connection point changed. It was no longer the law and family bloodline, it was the position of the heart, and connection to the promise of God in Christ. In all actuality it never was through the law and human bloodline, it has always been through the promise of God. In Christ the promise of God was seen in its fullness as a foretaste of things to come.
All that to say, any of us can be a child of promise. It matters not who our ancestors are. It matters not if they were faithful or not. Each of us can be a child of promise by holding to the promise of God as seen in Christ Jesus.