Proof of the existence of Imam of the Time and Hadith of two brother's Imamate (arguments and doubts)

Discussion of Imamate and particularly the Imam of the Time is an important issue and one of the major Shiite tenets, in a way that what distinguishes Shiite from other Islamic religions is the belief in the existence of Imam's birth and existence. One of the important responsibilities of the Shiites is defending this fundamental belief and one way of defending the faith, is to adhere to traditions that do not allow Imamate of two brothers after Imam Hassan and Imam Hussein (PBUH).From early on, there were people who have always raised doubts even unfounded, and have questioned the existence and the birth of this Imam which is like a rising sun. This paper also attempts to prove the existence of the, the Imam Mahdi with an analytical method, referring to the traditions of disallowing Imamate of two brothers after Imam Hassan and Imam Hussein (PBUH), and specifically respond to some doubts about the Imam Mahdi that Ahmad Katib, the author of Al-Imam Al-Mahdi: A Historical Fact or a Philosophical Hypothesis (Ahmad al Katib, 2007), have raised in denying the existence of Imam Mahdi (PBUH).Claims made by al Katib, are based on the argument he made about the traditions related to the lack of licensing Imamate of two brothers, that only Sheikh Tusi have raised two hundred years after the martyrdom of Imam Hassan Askary (the father of Imam Mahdi) and thus, he claims, cannot be a way to prove the existence of the Imam. Based on this current research, Shia scholars such as Ashari Ghomi (of Qom) have quoted those traditions in defence of existence and argued for it from earlier on, almost contemporarily with Imam Askary,. Thus, these traditions are not singularly referenced. Moreover, traditions also ascribed to the Imamate of Abdullah Aftah, which he claims, are not true.