There are two parts to the volturi. One is the volturi coven: Aro, Caius, and Marcus. The wives are (Aro)-Sulpicia, (Caius)-Athenodora, and (Marcus)-Didyme. Didyme is dead though.
The other part is the volturi guard: Alec, Jane, Chelsea, Afton, Corin, Demetri, Felix, Heidi, Renata, and Santiago.
Marcus, Caius and Aro everyone else considered part of the Volturi- besides the wives- are part of the Volturi Guard.
The Volturi come in Part two. Not both parts
vladmir is not part of the volturi, he is a vampire whose city was destroyed by the volturi centurys ago in the book
Aro is part of the Volturi, a powerful coven of vampires who enforce the laws and customs of the vampire world.
they are not like the cullens so they dont have last names they are part of the volturi "family". Volturi
The volturi
it's about renesmee and the volturi attack
Stephenie Meyer has not given enough information about Caius (or any other Volturi member, for that matter) for this question to be answered. No one really knows how he did become apart of the Volturi, though it would be interesting to find out.
The volturi come to kill renesmee and bella pushes the shield out of her to protect all the witnesses, and the volturi see that renesmee is human and they leave
They protect their daughter Renesmee against the Volturi.
I think the best part is when they meet the volturi (dc if its spelled rite) on the b-ball field
James is not a part of the valturi. James and Victoria and Laurent for that case were just nomads like most "regular" vampires who happened upon the Cullen family they had no direct links to the volturi until eclipse when Victoria makes her newborn army.