Chelsea

Chelsea is a vampire.

History
Chelsea, originally named Charmion, was born in Greece before 1100 BC, not long after the original Volturi members. Aro discovered her in the midst of the difficult time for the Volturi, sinc ehis brother-in-law, Marcus, failed to find the killer of his wife, Didyme, and became suicidal. Aro had Chelsea use her power to tighly bind Marcus to the Volturi. Since then, Chelsea became the linchpin in the Volturi as she keeps the other guards unified and the coven more functional. Because of her vital role, she often gets what she desires from Aro, who also uses Corin's gift to keep her in the Volturi.

Family Members

 * Afton (mate)

Powers and Abilities
Chelsea is gifted with the supernatural talent of influencing the emotional ties between people, either by weaking or strengthening them. Aro, one of the Volturi leaders, used her gift to keep Marcus loyal to the Volturi after Didyme's death. Due to the importance of her gift, Aro thinks of her as one of the high ranking members of the Volturi, along with Jane and Alce, and uses her as a secret weapon to disband their enemies and binding wanted people to the coven.

Source

 * Twilight Saga Wiki: Chelsea