Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Umm Kulthum bint Ali was the fourth child of Ali ibn Abu Talib (the first Shi''a Imam and fourth Sunni Caliph) and Fatima Zahra, the daughter of Muhammad. Umm Kulth m bint Ali was the 4th child of Ali and Fatima. Her believed marriage to the Caliph Umar al-Khattab is the cause of much contention between the Sunni and the Shiites. The reason for this is that Caliph Umar al-Khattab is considered to be a disrespected character by the Shi''as and therefore unworthy of the daughter of Ali, Even though, that Umm Kulthum bint Ali had a son from Umar named him Zayd ibn Omar ibn al-Khattab (famously known as Ibnul Khalifatayn; the son of the two Caliphs i.e. Umar and Ali), and a daughter named her Ruqayyah bint Umar.