Amun and his wife Kebi form part of the group of Cullen witnesses against the Volturi. Although Amun confirms the truth of Renesmee's nature, he doesn't want to get into a war with the Volturi. He's especially protective of Benjamin, his created son.
Benjamin is a very gifted vampire. He can influence the elements – earth, wind, and fire. He's a free-spirited person who sides with the Cullens, and doesn't approve of his creator Amun's possessiveness of him.