Kay

A.Amos,
Hmmm…Just venturing here, from the context surrounding vs.28 and continuing with vs.29 “And if you belong to Christ, then you are Abraham’s descendants, heirs according to promise.” It would mean that we are all one thing – heirs.
The circumsized Jew has not advantage over the Greek; the free person has no advantage over the slave; males have no advantage over females.

“The Spirit Himself testifies with our spirit that we are children of God, and if children, heirs also, heirs of God and fellow heirs with Christ” Rom. 8:16-17

We are all heirs through the Spirit – not physical means.