Delva,
I do not believe that ANDREW MCLUCKIE (bap 13.4.1740)who had children by ELIZABETH STEWART is the same ANDREW MCLUCKIE who married JEAN MEFFIN (METHVEN).
The ANDREW MCLUCKIE who married JEAN MEFFIN (METHVEN) is the brother of ROBERT MCLUCKIE and MARGARET MCLUCKIE. MARGARET MCLUCKIE married ROBERT BLAIR, brother of my 3xgr grandfather PETER BLAIR. This ANDREW was most likely baptised on 08 Aug 1749, in Drymen, Stirlingshire. (See below).
I have copies of letters written by ROBERT MCLUCKIE and other family members to MARGARET MCLUCKIE and ROBERT BLAIR in Barnet Vermont dating from 1786 to 1818.
These letter make reference to sibling John, Andrew, Christie, Elizabeth, Janet; the death of their father sometime shortly after March 1, 1788; the death of their mother "in the first of June 91"; and other family members.
A search of ScotlandsPeople showed a JOHN MCLUCKIE buried in Kippen Apr 05,1788 and the burial of JEAN (CHRISTIAN) GILFILLAN in Kippen June 09, 1791. This would lead me to believe that ROBERT and MARGARET's parents were JOHN MCLUCKIE and JEAN (CHRISTIAN) GILFILLAN.
OPRs and Associate Session records list the follow children of JOHN MCLUCKIE and CHRISTIAN GILFILLAN:
Janet - baptised 14 Feb 1748 in Drymen, Stirlingshire
Andrew - baptised 8 Aug 1749 in Drymen, Stirlingshire
Thomas - baptised 22 Jan 1753 in Drymen, Stirlingshire
_____ - baptised 5 Aug 1754 in Drymen, Stirlingshire
John - baptised 24 Jan 1756 in Drymen, Stirlingshire
I have not been able to connect the births of Robert, Margaret, Christie, or Elizabeth to JOHN MCLUCKIE and CHRISTIAN GILFILLAN but given the time period and the fact they were members of the Associate Session this does not surprise me. One of the four could be the unnamed child baptised 5 Aug 1754.
The letters also make several references to ROBERT and MARGARET's brother ANDREW and his family, including the fact that that ANDREW died Bet. 1802–1803 leaving 7 children: John, James, Robert, William, Jean and 2 other daughters. All five of ANDREW's children named in the letters are also children of ANDREW MCLUCKIE and JEAN MEFFIN (METHVEN). Their two addition children (Christian and Elizabeth) are almost certainly the two daughters not named in the letters.
As for your William who left for South Africa, Robert writes on 23 June 1818: "Andrews youngest son in clashhead William served his prentiship to be a couper and when he was ready with it the next trade was smugling and he was taken be the gagers two tims and he was obliged to flee for it he is away to the keep of good hope".
I hope this helps.
John