Hasan, the son of Muhammad bin Kiya belonged to the peasant family of Rudhbar. Historian Kamaluddin (d. 660/1262) writes in "Bugyat al- talab fi tarih al-Halab" that, "Muhammad bin Kiya had two sons, called Hasan and Hussain, whom he put in school with Rashiduddin Sinan, and gave these three an exact treatment that are needed for supporting the children." Hasan was a learned orator and eminent dai. With the courtesy of manner and eloquence words, he won over the greater part of the Ismailis in Rudhbar and Kohistan. He was a famous scholar, and wrote several books on Ismaili doctrines. It is related that a group of persons. failing to distinguish between Imam al- Kahir (also known as Hasan bin Muhammad) and Hasan, the son of Muhammad bin Kiya (also known as Hasan bin Muhammad), began to think the latter as their Imam. When his father Muhammad bin Kiya learnt the story, he assembled the followers of his son and said:- "This Hasan is my son, and I am not the Imam, but one of his dais." According to Marshall Hodgson in "The Order of Assassins" (Netherland, 1955, pp. 147-8), "His father at length had to refute this idea at a public meeting, showing that an Imam must be son of an Imam, which Hasan was not."
Muhammad bin Kiya is reported to have taken strict action to finish the rising faction propagating the imamate of his son and put 250 persons to death and expelled about same number of persons from the valley of Alamut. According to Farhad Daftary, "Eventually, Muhammad b. Buzurg-Ummid, who like his predecessors was rigid in his observance of the Shariah and the conduct of the dawa on behalf of the Imam, was obliged to take drastic action against the radical Nizaris who followed Hasan and believed in his imamate." (op. cit., p. 386).
Hence, Hasan also became apprehensive, and compiled treatises, asserting his innocence of such charge publicly. It seems improbable that once Hasan had asserted, then again would have claimed as an Imam after few years, since his assertations were not only verbal but in writing, which exercised as most trenchant source for a long time. Granted that Imam Hasan II was the son of Muhammad bin Kiya, then he must have refuted the treatises he had written in his father's time. His important treatises however, asserting that he was not an Imam, had been also destroyed with Alamut's library, making the field open for Juvaini to alter the history at his disposal.
It has been known that Hasan was not present during the celebration qiyamat-i qubra in Alamut in 559/1164 as he had been delegated to Syria by Imam Hasan II in 557/1162 as his hujjat, and where he is reported to have been killed in 560/1165 at Masiyaf.