Margaret and Robert married in late 1809/early 1810 according to the IGI on Familysearch. But there is a christening for a Katherine Anderson with those parents recorded in 1807. There are a number of births/christenings for Margaret Little aroung the 1780-90 mark.
Do you know when Margaret died? If it was after 1855, her parents' names should be recorded on her death certificate.
Nell