The Vengeance of the crown prince

Kim Taehyung was a illegitimate child of the emperor of the Daegu kingdom .
The only person he loved in his 25 years of life is his step brother Kim Seokjin
What will happen when the king and the crown prince of Wansan-gu kingdom killed his beloved brother . What will happen when Taehyung take over the throne of Daegu kingdom and seek his revenge by marrying the princess of Wansan-gu kingdom.