He prays that His own be with Him and see His glory. This chapter tells us much about the Word of God. This Word is the Father's gift to His Son. This Word reveals the true God to man, brings man to faith, preserves him in this faith and is absolute truth. 20 says that there is no revelation outside the Apostolic Word.
Christians are one in the faith.
Father, Son and Holy Ghost are one in essence. The two unities are analogical, not identical. Christ is in us by grace through faith. The Father is in Christ by nature. The two are analogical not identical.