Bahá'u'lláh intended to give His niece, Shahr-Banu Khanum, in marriage to His eldest Son, ‘Abdu’l-Baha. She was the daughter of His faithful older half-brother, Mirza Muhammad-Hasan. That was also the great hope of Mirza Muhammad-Hasan who hurried to Baghdad and pleaded with Bahá'u'lláh to bring about this union. But Mirza Muhammad-Hasan passed away before the Most Great Branch came of age.
When Bahá'u'lláh and His family were exiled to Iraq, Shahr-Banu Khanum remained in the district of Nur in Mazindaran, until in 1285 A.H. (1868) when Bahá'u'lláh instructed His uncle, Mulla Zaynu'l-'Abidin, to escort her to Tihran and from there to arrange her journey to Adrianople.
No sooner had this news reached Shah Sultan Khanum, a half-sister of Bahá'u'lláh and a follower of Mirza Yahya, than she arose in enmity and with the assistance of Mirza Rida-Quli, a half-brother of Baha’u’llah, and prevented the marriage from taking place. Mirza Rida-Quli, who had stood as father to Shahr-Banu Khanum after the death of her father, Mirza Muhammad-Hasan, was afraid that Násiri'd-Dín Sháh and his ministers would frown on this marriage and take him to task.
Shah Sultan Khanum took Shahr-Banu Khanum to her home in Tihran and practically forced her to marry instead Mirza Ali-Khan-i-Nuri, the son of the Prime Minister. Bahá'u'lláh has referred to this in Epistle to the Son of the Wolf. This marriage, so rudely imposed upon her, plunged Shahr-Banu Khanum into a state of perpetual grief and misery. Her youngest brother, Mirza Nizamu'l-Mulk, a faithful and devoted follower of Bahá'u'lláh, has recorded in his memoirs that after her marriage Shahr-Banu Khanum prayed fervently to God for her deliverance from her tragic plight. It seems that her prayers were answered, as shortly afterwards she became afflicted with tuberculosis and died.
(Adapted from ‘Baha’u’llah The King of Glory’, by Hassan Balyuzi, and ‘The Revelation of Baha’u’llah, vol. 2’, by Adib Taherzadeh)