Gali, we're on the same track. I spotted the Sarah McLarty-William Coutts-Agnes Wadlass Coutts connection too, and wondered if she might be the same Sarah as Sarah Douglas. However, there's this:
OPR Births Craignish, Argyll 508/00 0020 0045
SARAH CAMPBELL McCLARTY, daughter of DONALD McLARTY, tenant in ****(?) McLarty, Craignish, and JEAN McLARTY, his wife, was born on 29/5/1830, and baptised 8/8/1830.
This conflicts with:
(a) 1841 census - Sarah (Douglas) Coutts already had 3 children by then and is aged approx. 25. Sarah McLarty would have been only 11 years old that year, i.e. could not have 3 children.
(b) Stat. Marriages 1855 - Sarah Douglas Coutts remarried James Allardice - Sarah's parents' names are given as ALEXANDER DOUGLAS and SARAH CAMPBELL, i.e. not the same parents as Sarah McLarty's.
(c) Stat. Marriages 1865 - Alexander Coutts's marriage cert. (William Coutts's 2nd son) states that his mother's name was SARAH COUTTS nee DOUGLAS, i.e. not McLarty.
So they can't be the same Sarahs.
The fact that marriage certs are proving hard to find for a William Coutts and any Sarah, and lack of christenings for the eldest children suggests that they might not have been married at that time. I found a christening for MARY COUTTS at St. Vigeans Parish, 27/12/1847, born at Crossgate Road, daughter of WILLIAM COUTTS, a Weaver, and his wife, SARAH DOUGLAS. (Mary is the 5th child.) Sarah Douglas Allardice's death cert. (1871) also states that she was the first wife of William Coutts.
Looby, yes, I have seen the Ann Skea connection too. It looks like we can safely rule out William Coutts the tanner.
The William Coutts living in Greenock in 1841 sounds promising, given that his 2 eldest sons were born there c. 1834 and 1838. It suggests William might have returned to that area for work. The problem is his living arrangements in 1841 don't confirm who his parents were. My William was born at Murroes, Dundee in Angus (1851 census), which is nowhere near Greenock. I have searched OPR births at Greenock Old & West, Greenock East, and Greenock New and no William Couttses in the early 1800s.
OPR Births search for a William Couts born between 1810 and 1815 yield 5 results:
(1) parish of Keig, Aberdeen
(2) parish of Lerwick, Shetland
(3) parish of Dundee, Angus
(4) parish of Balmaghie, Kirkcudbright
(5) parish of Meigle, Perth
The only one that is remotely near Murroes is No. 3. And guess who the parents are? ALEXANDER COUTS & ISABEL LEITH! :-D
Grave plots at Arbroath might be an avenue to explore, given that family members were often buried in the same grave or nearby. If I can find the OPR deaths for Alexander Couts & Isabel Leith, they might tell me the grave no. or location.