Who is Christopher Ravena from Shattered Mirror and what is their importance?

Chistopher Ravena, Shattered Mirror, is truly Nikolas' twin. They are attending school at Acton with Nissa. Before he became a vampire he was living in the period right before the Civil War. When Nikolas was jailed for merder, Nissa changed him. Not wanting to be separated from his twin, Nikolas changes Christopher. The two brothers go on wild vampiric killing sprees.

Christopher falls in love with Sarah though he can't understand why he would. Later, he finds out that she's a daughter of Dominique Vida. He eventually ends up giving in to the heat of battle and changes Sarah into a vampire.