The chosen people of God are named in Isaac - children of promise.
"6 But it is not that the word of God has taken no effect. For they are not all Israel who are of Israel, 7 nor are they all children because they are the seed of Abraham; but, “In Isaac your seed shall be called.” 8 That is, those who are the children of the flesh, these are not the children of God; but the children of the promise are counted as the seed. 9 For this is the word of promise: “At this time I will come and Sarah shall have a son.”
Physical DNA benefits no one in the Kingdom of God.
Just a bit further in Romans the prophet Hosea is quoted:
“I will call them My people, who were not My people,
And her beloved, who was not beloved.”
26 “And it shall come to pass in the place where it was said to them,
‘You are not My people,’
There they shall be called sons of the living God.”
This comes full circle back to 1 Peter:
"But you are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light; who once were not a people but are now the people of God, who had not obtained mercy but now have obtained mercy"
The people of God were always people of promise. From faithful Abel to believing Abram, the Chaldean, to Christ. Now, all who are the sons of God, His own special people, are found in the Body of Christ. AND, we all come to our Father in the same manner - through the blood of His only Begotten Son.