Liu Qi
When Liu Xian (劉賢), the heir apparent of Wu, once made an official visit to the capital during Wen's reign, he played a board game called "liubo" with then crown prince Liu Qi, the future Emperor Jing. During a heated dispute, Liu Qi threw the game board at Liu Xian, killing him. This outraged his father Liu Pi (劉濞), the King of Wu and a nephew of Emperor Gaozu's, who was nonetheless obliged to claim allegiance to Liu Qi once he took the throne.