We still can't find a birth or christening for James (son of James & Jane?) but the 1841 census lists him with his wife of 2 months Ann (nee Jackson) and records that they were both born in Cumberland between 1812 & 1816 (because of the rounding). We also know that at the 1851 census Ann is a widow living as the head of the household with her three children John 9 , Margaret 6 & Ann 2, so James must have died between the birth of Ann and 1851. There is no recorded death in Whitehaven so being a mariner James jnr could have died anywhere. Ann later marries a Thomas Killip 1852 in Whitehaven.
That doesn't help your William enquiry much but we have requested a copy of the 1846 Jun qtr death certificate of Jane Callow in Whitehaven to see if she is Jane Quine wife of James.
Further, did you ever see the posting of a message by Clive Callow on genforum.genealogy.com/callow/messages on 01Dec1999 saying that James Callow married Jane Quine in Lonan IOM 28 Nov 1812 and had 2 children in Lonan IOM -Margaret chr. 5 Sept 1813 & Ann chr 2 Jan 1815. If James & Jane are also the parents of James (m Ann Jackson), then James & Jane appear to have had 6 children. This would explain the apparent gap between their marriage 1812 and the later recorded Whitehaven children being born the the 1820's. Does anyone have any thoughts on ths?
While James jnr cites Cumberland as place of birth in the 1841 census he is of an age to have been born at the time they moved from IOM to Whitehaven and may explain why a record of a birth/christening can't yet be found.
On the 1841 Whitehaven census Margaret, Ann & James jnr are not listed with their parents James & Jane like other children William, Ann & Thomas, as they would have been old enough to have left home as in the case of James jnr to marry and be listed separately. In the case of Ann born on the IOM, she may have died and they have re-used the name again for a younger daughter Ann b1823.
We will confirm the details of the Jane Callow death certificate to let you know if it confirms the nee Quine issue.