In verses 18 and 19 Paul is talking about our Christian lineage, For through him we both have access to the Father by one Spirit. Consequently, you are no longer foreigners and aliens, but fellow citizens with God’s people and members of God’s household. Since Christ died for the sins of the world, it included those people who are not necessarily of Jewish heritage. The beauty is this now includes the rest of us. This is our gentile heritage, and we are now the equivalent of God’s chosen people as citizens of His kingdom.