Your query is sure fire a puzzler.
I think we may have corresponded in 2006 about this but can't be certain.
I thought I was making headway, and it might still be correct, but something reared its head.
Could you tell me which one of Isaac and Sarah's children you descend from.
I have found the family on 1841,1851,1861 and 1871 census records and then I found the attached info on the IGI.
Does it mean anything to you ?