Original sentence: Shi'a Muslims believe that Ali ibn Abi Talib, Muhammad's cousin and son-in-law, was the rightful successor to Muhammad, and his descendents, the Shi'a imams, to be the leaders of the Muslim community
Edited sentence: Shi'a Muslims, a sect of Islam, believe that Ali ibn Abi Talib, Muhammad's cousin and son-in-law, was the rightful successor to Muhammad, and the ancestor of the Shi'a imams, whom the Shi'a believe to be the divinely ordained spiritual leaders of humankind