Deatils of the family are here: http://homepages.rootsweb.ancestry.com/~cmddlton/dglss1.html with indications that they are ancestors of the Countess of Strathearn (as she is known in Scotland), Kate Middleton, wife of Prince William. I have not been able to discover what the links are!
Nothing on Daniel (?born Donald) or Effie's parents, though.
Kate Middleton does have a Douglas ancestor: http://www.douglashistory.co.uk/history/articles/kate_middle... .
However, there may be something in "Scattered Seed - Genealogical Research Data of Southeastern North Carolina" - Bridges indicating that Daniel Douglas, son of Robt. and Margaret McCutcheon Douglas was born abt. 1735 Glasgow, Lanark, Scot.,
died 1816 Richmond County, No. Carolina Daniel m. Effie McLean.
Maybe the marriage was in the Isle of Skye?