The Báb’s father passed away early during His childhood

According to Mirza Abu'l-Fadl-i-Gulpaygani, Siyyid Muhammad-Rida, the Báb'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 Bab 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 Babi-Baha'i Faith in Shiraz by Haji Mirza Habibu'llah-i-Afnan, [1] Siyyid Muhammad-Rida passed away when his son was nine years old, and 'Abdu'l-Baha appears to confirm this account. [2] 

- Balyuzi  (‘The Báb, Herald of the Day of Days’)

[1] Haji Mirza Habibu'llah's father, Aqa Mirza-Aqa, was a nephew of the wife of the Bab, and his paternal grandfather, Aqa Mirza Zaynu'l-'Abidin, was a paternal cousin of the father of the Báb

[2] ‘Abdu’l-Baha, ‘A Traveller's Narrative’

The Báb was a young merchant of the Pure Lineage. He was born in the year one thousand two hundred and thirty-five [A.H.] on the first day of Muharram, [October 20, 1819] and when after a few years His father Siyyid Muḥammad-Riḍá died, He was brought up in Shíráz in the arms of His maternal uncle Mírzá Siyyid ‘Alí the merchant. 
- ‘Abdu’l-Baha  (‘A Traveler’s Narrative’)