In the Kenyon church records I have a Donald McDonald married to Flora Urquhart with a Daughter Mary McDonald born in 1849. The information is from Mary's marriage record to Duncan McIntosh. So either Donald was married twice and Mary and Angus are half siblings or your information on Christy as Angus' mother is incorrect. Here is a link to the marriages in Kenyon.
http://glengarry.tripod.com/marrkpd.html
I am related through the McIntosh side.
Hope this helps..Katie