1841 census gives a pointer to what is going on here. The family of James Kerr and his wife Margaret is listed, but there is no sign of a Catherine Kerr or a Catherine Kinross Kerr, however there is a servant listed a Margaret Kinross age 30. They are living at Broad St, Stirling.
James Kerr age 45, Margaret Kerr his wife age 40, and children
William Kerr, 15
Isabella Kerr 13
Jane Kerr 9
Agnes Kerr 7
Mary Kerr 4
Janet Kerr 2
Plus Margaret Kinross, age 30 a servant