Sutherlands in Lairg

[fredacole]

In 1855 John Gunn married Mary Anne Sutherland. Her parents were John Sutherland of Berridalle and Anne Matheson of Lairg. John & anne married in Lairg 15 May 1813.
Sons William, Duncan, Donald, Alexander, David, Finlay were born  between 1813 and 1824 in Lairg and Creich.
Two daughters  Christy born 1816 in Dornoch and Mary Anne born 1931 in Berridale.
 Mary Anne is my G.G. grandmother.
My problem is I haven't been able to find her brothers or sister either in Family Search or in Scottish census.
I have had to presume this is the correct family as the only marriage I could find of her parents  in Caithness or Sutherland was the above
Can anyone help please?     Freda