As of now, Lucian's father, Julian Kiev is the king. The order of succession is as follows: 

1. Rowan (29) MARRIED WITH 2 BABIES

2. Colton (26) PLAYBOY

3. Adrien (25) MARRIED WITH 1 BABY

4. Xavier (22) MARRIED

5. Xander (22) SINGLE

6. Darius (20) ENGAGED 

7. Lucian (15) SINGLE

8. Soren (14) PLAYBOY (Or so he says...)