This means it is not the children of the flesh who are the children of God; rather, the children of promise are counted as descendants.

The Spirit himself bears witness to our spirit that we are God’s children.

nor are all the children Abraham’s true descendants; rather “through Isaac will your descendants be counted.”

And if children, then heirs (namely, heirs of God and also fellow heirs with Christ) – if indeed we suffer with him so we may also be glorified with him.