Wow! Can't believe I got such a quick reply! Been going round in circles for months on this one as couldn't work out how Eliz could have two surnames. I have today found a marriage on Scotland's People for David Arbuthnot and Mary Burnett in Montrose on 31 Jan 1841 (OPR. Marriages 312/00 0110 0294 Montrose), so think perhaps Eliz's maiden name was, in fact, Arbuthnot. However, it looks likely her mother married again in 1846 to William Robertson when Elizabeth would only be around 2. Possibly Eliz and her older sister, Mary, were both children of David Arbuthnot and Andrew, their brother, born around 1850, was William's son. The girls may have taken on their stepfather's surname for convenience sake. Does this seem plausible, Annette? Thank you all for your experience and for taking the time to help me. I'm so pleased!!