Parallel
Romans 9:8
Robinson-Pierpont Byzantine Textform · Berean Standard Bible
Τοῦτ’ ἔστιν, οὐ τὰ τέκνα τῆς σαρκός, ταῦτα τέκνα τοῦ θεοῦ· ἀλλὰ τὰ τέκνα τῆς ἐπαγγελίας λογίζεται εἰς σπέρμα.
So it is not the children of the flesh who are God’s children, but it is the children of the promise who are regarded as offspring.