Hi Suzi
Just double checking whether you already have this information from IGI for Christina Bell McNaught, Richard's mother.
There's one marriage showing on IGI which may be for parents David McNaught and Janet Porteous on 26 Nov. 1861 in Ochiltree, Ayr. Children to a couple with these names are given as:
1. Jane Bowman McNaught b.20 Mar 1862 Ochiltree, Ayr
2. Christina McNaught 29 Oct 1866
3. Janet McNaught 30 Oct 1868
4. Richard Porteus McNaught 21 Feb 1872
5. Chirstina Bell McNaught 30 Jan 1874
The last four are showing as born in Colvend, Kirkcudbright.
Regards.
Monica