Hi Christi, I think I have figured out how the Fergussons of Mulberry Grove connect to the Fergussons of Craigdarroch. That would be by William Fergusson, messenger of Moniaive: http://dna.cfsna.net/GEN/Dumfries/William_F_Moniaive.htmlhttp://dna.cfsna.net/GEN/Dumfries/William_F_Moniaive.html
John Fergusson whose Testament Dative and Inventory isdated 20 Apr 1687 and therein states that he is "brother-german to the deceased Robert Fergusson of Craigdarroch". The testament mentions a Sarah Fergusson. This document is refered to in Records of the Clan, p.435, and is interpreted that John had a son William and a daughter Sarah. http://www.archive.org/details/recordsofclannam00ferghttp://www.archive.org/details/recordsofclannam00ferg
Connecting the dots one concludes that William Fergusson, messenger of Moniaive, is a grandson of William Fergusson, and Sara Grierson daughter of Sir William Greirsoun of Lag [Lagg]; their marriage contract is dated 9 May 1621.
This opens up two more leads towards finding a living male Fergusson descended from the Fergusson of Craigdarroch, namely what became of Alexander Fergusson born 13 Jul 1712 and John Fergusson christened 17 Sep 1725?