Just checked the 1861 census for the Williamsons:
East Lormsdale 37 6 page 5
William Williamson , 36, farmer of 10 acres, b. Halkirk
Elizabeth, 34, b. Halkirk
Janet Williamson, sister ,24
Alexander McLeod, 18, brother in law
William W Sutherland, 2 month, nephew
Gadget
Added - I think the Sarah -> Esther became Elizabeth or it was Janet
