When we accept Christ and His sacrifice for us He then puts His Spirit in us, the Spirit of Love, the Holy Spirit. The Holy Spirit is our unity with God, our bond with God. We now share the same Holy Spirit that unites the Father and the Son, the same Spirit that makes God One, also makes us one with God. But he that is joined unto the Lord is one spirit. (1st Cor 6:17) If we do not have the Holy Spirit than we are not part of Gods family, we are not blood relatives of Christ. But you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. Now if anyone does not have the Spirit of Christ, he is not His. (Rom 8:9) But not only do we need to have the Holy Spirit but we must also be led by the Holy Spirit. For as many as are led by the Spirit of God, these are sons of God. (Rom 8:14)