Caliph Al-Hasan ibn ‘Ali is the grandson of which Islamic prophet?
Mujtaba Al-Mujtaba (Arabic: اَلْـمُـجْـتَـبَى‎ ‎ ) is an Arabic word which means "The Selected One" or "The Chosen One among many." It is a title of the Islamic "Nabi" (Arabic: نَـبِي‎ ‎ , Prophet) Muhammad, and his grandson, the Caliph Al-Hasan ibn ‘Ali.
Al-Mu'tasim Abū Isḥāq Muḥammad ibn Hārūn al-Rashīd (Arabic: أبو إسحاق محمد بن هارون الرشيد‎ ‎ ; October 796 – 5 January 842), better known by his regnal name al-Muʿtaṣim bi’llāh (المعتصم بالله , "he who seeks refuge in God"), was the eighth Abbasid caliph, ruling from 833 to his death in 842. A younger son of Harun al-Rashid, he rose to prominence through his formation of a private army composed predominantly of Turkish slave-soldiers ("ghilmān"). This proved useful to his half-brother, Caliph al-Ma'mun, who made use of al-Mu'tasim and his Turkish guard to counterbalance other powerful interest groups in the state, as well as employing them in campaigns against rebels and the Byzantine Empire. When al-Ma'mun died unexpectedly on campaign in August 833, al-Mu'tasim was thus well placed to succeed him, overriding the claims of his nephew, al-Abbas ibn al-Ma'mun.