The CW series has cast Caspar Zafer and Nathaniel Buzolic as the two remaining members of the Original vampire family, TV Guide reports.
They will play the roles of Finn and Kol respectively. The two brothers will first appear in episode 13 of season three.
Previous Original family members who have appeared include the hybrid Klaus (Joseph Morgan), his brother Elijah (Daniel Gillies), his sister Rebekah (Claire Holt) and his father Mikael (Sebastian Roche).
Morgan recently revealed that he would love Klaus and Elijah to clash on the show, adding that a showdown would be exciting.
Vampire Diaries executive producer Julie Plec has said that Damon will rethink his feelings for Elena when The Vampire Diaries returns, claiming that Stefan's (Paul Wesley) behaviour will lead Damon (Ian Somerhalder) to reconsider acting on his desire for Elena.
The Vampire Diaries will return January 5 on The CW at 8pm.