This keeps getting more interesting every day...
Jamaican Christening records available on familysearch.org appear to indicate that our Campbells got baptized en masse:
- Mary, Lillie, Jane, Ann, Isabella and Iver Campbell were all Christened in Hanover on 10 Dec 1803, along with their mother Elizabeth Malcolm Campbell and 2 or 3 other Campbells: Amelia, Catharine, Nancy (probably same as Ann). I suppose that could mean that the "Mrs. Campbell Endeavour" mentioned in the will could be Amelia or Catharine as a married adult?
- Alexander Campbell and Sarah Campbell were both Christened in Hanover on 30 Sep 1809; in these two records, the mother's name was specifically given as Elizabeth Malcolm Campbell. I therefore suppose "Sarah" must have been Margaret. (That's very easy for me to believe; to this day I'm still not 100% sure if my great-grandmother was Sarah Margaret Walker or Margaret Sarah Walker!).
I suppose other explanations are still possible, but this all sounds like one big happy family to me (except for Iver, whom I suppose may have had a different mother)... a little lax in their church attendance, though!

Tim (getting very curious about a DNA test...)