Siyyid (or Mirza) 'Ali-Muhammad, known to history as the Báb, was the son of Siyyid (or Mir) Muhammad-Rida, a mercer of Shiraz [Persia]. He was born on October 20th 1819 (Muharram 1st, 1235 A.H.). Through both His father and His mother He was descended from Imam Husayn, the third Imam. Thus He stood in direct line of descent from the Prophet Muhammad. According to Mirza Abu'l-Fadl-i-Gulpaygani [a renown Baha’i scholar], Siyyid Muhammad-Rida, the Bab's father, died when his only child was an infant, unweaned. Then the care of the child devolved upon a maternal uncle, Haji Mirza Siyyid 'Ali. He was the only relative of the Báb to espouse His Cause openly during His lifetime and, as will be seen, to accept martyrdom for His sake. But according to a manuscript history of the Bábí-Bahá'í Faith in Shiraz by Haji Mirza Habibu'llah-i-Afnan,[1] Siyyid Muhammad-Rida [the Bab’s father] passed away when his son was nine years old, and 'Abdu'l-Bahá appears to confirm this account.[2]
[1] Haji Mirza Habibu'llah's father, Aqa Mirza-Aqa, was a nephew of the wife of the Báb, and his paternal grandfather, Aqa Mirza Zaynu'l-'Abidin, was a paternal cousin of the father of the Báb.
[2] Browne (ed.), A Traveller's Narrative, Vol. II, p. 2.]
(H.M. Balyuzi, The Bab - The Herald of the Day of Days, p. 32)