Have you looked for wills of any Helliwell/Hellewell family members - not just those named David.
How about the Wilkinson Family did they leave any wills?
They can be very useful with names of children and nephews and nieces.
One thing I did notice Charles Helliwell widower married Grace RILEY 1795 at Elland
When David married Susy Mansley 1805 a witness was Thomas RILEY.
I'm leaning towards Charles being David's father, as his first son is Charles. David himself was a weaver, but his sons Charles and Aaron were masons/ stone masons.
Found so far children of Charles and Phillis Helliwell- St John the Baptist, Halifax
John 1781-1787
James 1783
- gap of 7 years*** when David could have been born-Keep in mind a stone mason might have to travel for work, not every job would be on his door step.
Benjamin died 1790
Betty bap. November 1791 died 1792
Charles died 1794
Charles died 1795
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As far as the children of David goes you are only listing those from the 1841 census.
I gave you the other children
William 1818-1839 ref; Tombstone/Memorial
Susey 1831 1832 same
Stephen 1823 -1833 same
Eli bap 26 August 1821 not mentioned on the memorial/tombstone - need to find out more about him.