sentences:  Later during the 12th century some of Nizar's actual or claimed descendants tried, without success, to seize the throne from the Fatimid caliphs.Nizar was born on 26 September 1045 to the ruling Fatimid imam–caliph, al-Mustansir ().At that time, al-Mustansir was around 15 years old and had already been on the throne for ten years.