Annas being high priest, and Caiaphas — There could be but one high priest, strictly speaking, at once. Annas was the high priest at that time, and Caiaphas his sagan or deputy.
Related Commentaries of Luke 3:2
Luke 3:2
2 Annas and Caiaphas being the high priests, the word of God came unto John the son of Zacharias in the wilderness.