Gloria,
And I'm sure we'll go over it again
I have a Robert Kippax son of Robert and Betty, born Haggate, christened St Bartholomews, Colne 5th Feb 1764, so he was alive around then.
This chap would appear to be the son of Sarah's Great Grandfather. I hadn't come across this reference before! This places him as a sibling of:
Joseph (bap 06 DEC 1761 Burnley)
Susan (20th Feb 1767 Susan d Robert Kippax of Haggate bap. same time as cousin John s. James)
Tabitha (1769 Aug 17th Tabitha d Robt Kippax of Haggate bap. same time as cousin Joshua s. Susan)
So 'old' Robert is still around by 1769 as is, presumably, his wife, Betty Skelton (of whom I know nothing more!)
My belief is that this 'old' Robert, like your James (1719-1769) are two of the children of Edward K (the bastard son of Edward K and Grace Simpson)
Shoot me down if you wish, but I think this all ties together quite nicely