1) Believing that Jesus is the Christ means believing he is the Messiah prophesied in the Old Testament, and receiving him as the anointed one sent by God to be prophet, priest and king.
2) Anyone who has this true, heartfelt faith in Jesus as the Christ has been spiritually begotten by God and is therefore born of God.
3) Likewise, anyone who loves God their heavenly Father will also love others who are born of God - fellow Christians who share the same divine Father. Loving other Christians is a natural consequence of loving God.