I haven't followed up on Isabel's line yet.
David's will contains an unusual clause, which, I suspect, would be interesting to investigate:
"... my daughter Isabel remain in the care of her aunt Mary Ann ROLFE ..."
I haven't worked out where Mary Ann might fit in.
David's brother, John, had a daughter Mary Ann.
I haven't yet found names for the wives of the other brothers.
And I haven't tracked down any of David's sisters.
Perhaps you can shed some light on Isabel and her Aunt ?