Hasan bin Hasan was Imam Hasan Mujtaba's second son. His mother was Khawla who was the daughter of Manzur Fazariyah.[1] Hasan bin Hasan better known as Hasan al-Muthanna was a nobleman, a virtuous and God-fearing son of the second Imam (AS). He was in charge of alms given by Imam 'Ali (AS). He took part in the rebellion of 'Abd al-Rahman bin Muhammad against Hajjaj bin Yusuf[2]. It is said that he lived until the time of Abdul Malik bin Marwan's government. He was present in the event of Karbala alongside his uncle, Imam Hussein (AS).
According to reports by some reporters, Hasan al-Muthanna was martyred in 97 A.H. in the time of Sulayman bin Marwan's government. It seems from historical accounts that he lived 53 years.  Keeping in view these dates, it can, therefore, be said that he was 17 years old in the event of Karbala.[3] Thus, considering that Hazrat Qasim is said to have been 13 years old on the day of Ashura, we must say that Hasan al-Muthanna was four years older than Qasim. He did not fall short of defending his Imam. Although according to some sources, Hasan bin Hasan was thirty five when he died, it seems a mistake has taken place in the dates[4] in the sense that the number 53 has been mistakenly placed as 35.
Hasan bin Hasan was among the captives of Karbala. He had been injured in the battle. It is said that Asma bin Khareja separated him from among the captives and took care of him. As for Hasan al-Muthanna's marriage, it has been reported that he asked his uncle, Imam Hussein (AS) for the hand of one of his daughters in marriage to him. The Imam replied: "Choose one of my two daughters whom you like to marry." But Hasan al-Muthanna did not respond on account of modesty. Imam Hussein (AS) chose Fatima[5] for him and said: "She is more like my mother Hazrat Fatima (SA) than any other of my daughters."[6] After his death, his wife erected a tent on his grave and she engaged in worshipping for a year." Hasan bin al-Hasan never claimed to be an Imam and no one has claimed that he was an Imam.[7]
Sayyid bin Tavus writes about the merit and nobility of Hasan bin Hasan and some other children of Imam Hasan (AS): "These are people whose lofty position and merit all Muslims acknowledged".[8]
According to a part of a narration reported from Imam Reza (AS) about the continuation of the offspring of Imam Hasan and Imam Hussein, peace be upon them, it is inferred that Hasan al-Muthanna had many children and Imam Hasan's offspring continued through him and another brother of his named Zaid. It has been reported in this tradition: "Hasan bin Ali's offspring continued through two of his sons named Zaid and Hasan. Zaid had a son whose name was Hasan. Also, Hasan al-Muthanna had sons named Abdullah, Ibrahim, Dawood, Ja'far and Hasan, better known as Hasan asl-Muthallath, who continued a third generation of Imam Hasan (AS)."[9]

---