Hassan (a.s.) and Hussain (a.s.) are the leaders of the Youths of Paradise.
  

Hussain (a.s.) is from me and I am from Hussain (a.s.) , Allah befriends those who befriend Hussain (a.s.) and He is the enemy of those who bear enmity to him.
  

Whoever wishes to see such a person who lives on earth but whose dignity is honoured by the Heaven dwellers, should see my grandson Hussain (a.s.).
  

O my son! your flesh is my flesh and your blood is my blood, your are a leader, the son of a leader and the brother of a leader; your are a spiritual guide, the son of a spiritual guide and the brother of a spiritual guide; you are an Apostolic Imam , the son of an Apostolic Imam and the brother of an Apostolic Imam; you are the father of nine Imams, the ninth of whom would be the Oaim (the last infallible spiritual guide).
  

The punishment inflicted on the murderer of Hussain (a.s.) in Hell would be equal to half of the total punishment to be imposed on the entire sinners of the world.
  

When the Holy Prophet (phuh&hf) informed Hazrat Fatimah (s.a.) of the Martyrdom in store for his grandson, she burst into tears and asked, "O my father! when would my son be martyred?" "In such a critical moment," he replied," When neither I nor you, nor Ali would be alive. " This accentuated her grief and she inquired again," Who then, O my father, would commemorate Hussain's martyrdom?". The Holy Prophet (pbuh&hf) said, "The men and the women of a particular sect of my followers, who will befriend my Ahlul-Bayt, will mourn for Hussain and commemorate his martyrdom each year in every century."

source : http://www.warispak.com