The online death index in 1858 for Frances has her aged 73 so getting closer to the age of Fanny 1781. Hoping against hope informant is a child but not James or Eliza.
She is on the 1841 census at brick lane wrongly indexed as Whiteaker (or some such) with Eliza Whitehead 20 and Henry 20 and Henry 15 but the Henry 20 doesnt exist
James being executor for his father and getting letters of Administration for Frances, I would think would be oldest son
Son George baptised 1820 with birth date of 1810, could well be the George Whitehead also a baker, who married Elizabeth For(e)man in 1832 and died in 1868, Census records have him being born at Diss, (1807-1810) The George Street address on baptism would be where parents were at time of Baptism.
No record of James Whitehead's birth and his age from Census and death records are 1805-1814
Eliza was born and baptised in 1819
Robert 1821
Robert 1823 baptised 2nd January 1837 father was deceased. Not on 1841 Census (that i can find)
Henry born and bapt 1824, witness in 1844 on sister's marriage, (I have not found any other record for him)
So IF the couple married in 1807 and James is first child, there could well be several other children who survived or didn't up until Eliza in 1819
Colin