I noticed a few things...
There's a matching-style gravestone for William Babcock b. 1798 in Longwell-Drew Cemetery. Could be John's brother. In Census's James and William appear to have farms quite close to one another later in life. This is the 1870 US Census at Vernon, Sussex, NJ. Image 7 and Image 6. James is listed as "Jas.":
On William's FAG memorial it says his parents were Stella and James Babcock (citing Vernon Death Records) . Of course, I can't seem to find Stella and James Babcock/Badcock to loop back to see if they have a son named James. Maybe someone else can find them?
Another thing I noticed is James's wife Hannah Conklin has a mother who was born as Hannah Babcock and a step-mother born as Charity Babcock who was the sister of Hannah's mother. So Hannah Conklin could have been a cousin to her husband James Babcock, but I can't find Hannah and Charity's family either....both married Thomas Conklin.
Some people seem to connect those sisters back unsourced to the Haverstraw NY group of Babcocks that were intermarried with Conklins. And some claim the mother Hannah was born at Fort Monmouth NJ, which happens to be near where the Thomas Babcock group Seventh Day Baptist colony was manufacturing salt....but none of this has evidence. lol!