I can confirm that the burials of William & Mary in 1748 & 1751 were indeed the children of James & Martha.Also their last son Thomas was the child buried on 11/11/1772 so that thefather of family 5 must have been a grandson of James & Martha.I can't, however, find a baptism in Netherthong Weslyan but maybe the fiche doesn't go back quite early enough.I can't find a record corresponding to the index entry for the burial of Thomas Knutton? in 1774.
Martha was buried on 18/11/1777.The KB register was being uncharacteristically informative at this time.It records that she was the wife of James Knutton of Thurstonland Mill and daughter of John Roebuck of ?Hollingreave and that she died on the 16th with the cause given as "sudden death".
The James buried on 16/5/1788 is described simply as of Mytham Bridge with no parentage given so it appears that he was the original James, father of family 1 & not the son of family 4.
The Sarah and the un-named child buried in 1782 and 1783 are indeed the children of William and thus belong to family 4 which makes the gap in family 2 all the more conspicuous.
Finally there is the following entry for Kirkburton:
"Sarah and Mary daughters of James Knutton of Mythambridge in Thurstonland the one aged 23 years and the other 28They died on the same day and at about the same hour of the day and were buried in the same grave."