Sima Daozi
In 397, Emperor Xiaowu was killed by his concubine Honoured Lady Zhang, after offending her. However, with the emperor's only brother Sima Daozi, Prince of Kuaiji, being incompetent and Crown Prince Dezong being developmentally disabled, no investigation into Emperor Xiaowu's death was conducted. Crown Prince Dezong succeeded to the throne as Emperor An, and Sima Daozi became regent.