Is it true that the Prophet, may God’s prayers and peace be upon him, informed Al-Hasan and Al-Husayn of their deaths, and is it confirmed that their killers are in Hellfire?

Al-Hasan and Al-Husayn are the masters of the youth of Paradise, and love for them is a part of faith. Al-Husayn was martyred in Karbala, and the Prophet (peace be upon him) foretold his killing. As for Al-Hasan, he died naturally, as people die, and his death by poison is not established. The killers of Al-Husayn were people of corruption and injustice, and their affair is with Allah. It is not established that the Prophet kissed Al-Husayn's neck and said, "You will die slaughtered," or kissed Al-Hasan's mouth and said, "You will die poisoned"; rather, these are fabrications. The Rawafid (Shi'a) are among the most mendacious sects.