Eleazar and Carmen are the first of the Cullen friends to arrive in Forks to support them against the Volturi. Carmen almost immediately takes to Renesmee and vows to do anything to protect the baby and to fight for the truth.
Eleazar, Carmen's husband, used to be part of the Volturi guard due to his sensitivity to the gifts of other vampires. He identifies Bella's shield and encourages her to expand it. He also realizes that the Volturi have come not to do justice, but to destroy the Cullens and to acquire gifted family members.
There has been bad blood between Irina and the Cullens since the werewolves killed her friend Laurent to save Bella. She also saw her mother die at the hands of the Volturi for creating an immortal child. When she sees Renesmee with Jacob, her anger and sense of justice propel her to go to the Volturi and accuse the Cullens of breaching vampire law by creating an immortal child. Faced with the truth on the field of battle, she admits to her mistake, but is immediately executed by Caius.
Kate comes to be a witness for the Cullens against the Volturi. She has a special defensive gift to send electric shock through her whole body, which she developed with long practice. She takes it upon herself to train Bella and helps her expand her shield. She tries to attack the Volturi for killing her sister Irina, but is stopped by Garret.
Tanya comes to be a witness for the Cullens as well. She feels guilty about what her sister Irina has done and pledges her allegiance to the Cullens in the event of a fight.