Bondservant. See on Mat 20:26; see on Mar 9:35; see on Rom 1:1.
Then an heir (καὶ κληρονόμος)
Καὶ marks the logical sequence. Comp. Rom 8:17. The figure is based upon Roman, not upon Jewish, law. According to Roman law, all the children, sons and daughters, inherited alike. According to Jewish law, the inheritance of the sons was unequal, and the daughters were excluded, except where there were no male heirs. Thus the Roman law furnished a more truthful illustration of the privileges of Christians. Comp. Gal 3:28.
Of God through Christ
The correct reading is διὰ θεοῦ through God, omitting Christ.