Complex sentence: However, it is controversially believed that Ismā'īl predeceased his father, and that Jafar A'Sadiq said,'My successor will be Musa Qasim', although his closest supporters believed Ismail had gone into hiding to protect his life.
Split into simpler sentences: However, it is controversially believed that Ismā'īl predeceased his father. His closest supporters believed Ismail had gone into hiding to protect his life.