Imam Hasan (AS) and Imam Hussain (AS) were two brothers and at the same time Imams. In that period and age both were Imams one obeyed the other; the younger brother obeyed his elder, as he became Imam. Imam Hasan (AS) actually held the political authority as well as the religious one. He administered social affairs and held the government over them. Imam Hussain (AS) had no say as long as his brother Hasan was alive. The writer now tries to establish a link on this precedent and suggests that the Imamate was of Abdulla Ajta instead of Mosa al-Kadum or to the both of them and similarly to Jafar brother of Imam Hasan Askari. The office of Imamate is Divine.
As such, the Imamate is not dependent on our pleasure. It is not our right to suggest one for the Imamate or not to approve the others. When Mosa al-Kadum became Imam, Abdullah goes out of question. Likewise Jafar is not Imam because Hasan Askari is the Imam. The Imamate of Hasan and Hussain can not be a base for any who happens to be a brother of the Imam to become Imam. To avoid such a kind of mischief or this type of interpretation the Prophet (SAW) in his life time had repeatedly disclosed the names of the Imams individually. He had even specified the characteristics of them. So, that neither doubt nor suspicion would remain.
Adapted from: “A Reply To Belief Of Mahdism In Shia Imamate” by: “Ayatollah Lutfollah Saafi Golpayegani”