I think that the only connecting fact is that the children are all the children of John Thornton of Armley with no mother's name being listed. I cannot see any hint of an occupation, which would help to perhaps unite or split the family/ies. However, the baptism of John Thornton in 1761, son of William, does not quite fit - as you say he would only have been 12 (assuming he was baptised as a baby). I'm also wondering what the notation is after John Thornton's burial entry in 1798 - other entries for males on the same page are shown as "M Man" and "Wid'r"

A little perplexing to say the least.