Re Joe's find of Rebecca LAURANCE bap 1820, father John (presumably the 18yo Rebecca with 'our' CLARK family in 1841).
Looking at the IGI for other LAURANCE children in Lonmay with father John, and comparing the names with those in Lonmay in FreeCEN, it is probably the LAURANCE family in the 1841 at Craigellie, Lonmay - John not there but family has Eleonora 54, George 25, Eleonora 23, Jean 20, Robert 17, Christian 12.
The following extracted marriage in the IGI possibly is the relevant one:
John LAURANCE m Eleonora SHAND, 21 Sep 1806, Rathen
1851 has, at Nether Tyahesnook Lonmay, George 40 b Rathen (he's in the IGI, b 1811, mother's name actually listed!), mother Eleanora S 65 b Rathen, sister Eleanor 38, sister Jean 28, brother Robert 27, servant (presumably sister) Christian 23 all b Lonmay.
John LAURENCE & Eleonora SHAND had (all extracted entries):
In Rathen
*Isabel LAURENCE bap 8 Jan 1807
*William LAURENCE bap 4 Mar 1810
*George LAWRENCE bap 25 Dec 1811
- George LAWRENCE also listed in Rathen as bap 5 Jan 1812
*Eleanor LAWRENCE bap 2 Nov 1813
- also listed in Lonmay as Helenora LAURANCE bap 22 Nov 1813
*John LAWRENCE bap 1815
*Joseph LAWRENCE bap 4 Jul 1815
- also listed in Lonmay as Joseph LAURANCE, same date
In Lonmay (mother's name not listed)
(*Helenora LAURANCE bap 22 Nov 1813 - see above)
(*Joseph LAURANCE bap 4 Jul 1815 - see above)
*Mary LAURANCE bap 18 Jun 1817
*Rebecca LAURANCE bap 1 May 1820
*Jean LAURANCE bap 20 Apr 1822
*Robert LAURANCE bap 23 Mar 1824
*Elizabeth LAURANCE bap 18 Mar 1826
*Christian LAURANCE bap 26 Mar 1828
All this suggests that 'our' Isabella (LAURANCE) CLARK might be a daughter of John & Eleonora, and thus sister of Rebecca LAURANCE (18 in the 1841 in the CLARK household).
JAP