Thanks for so much information in your reply MonicaL.
I have done a lot of work on this story of the Melbourne Flemington as I wrote an entry in the Encyclopedia of Melbourne on it's naming, and caused a stir. It was obviously named after Flemington Estate of James Rose esq. in Scotland, Elizabeth's father, not the butcher named Fleming as had long been supposed.
A document in the State Library of Victoria claims Alexander Hunter (sen) and James Watson (sen) were boyhood friends, meeting in later life and organising the pastoral concern in which their sons and some Hunter cousins were involved. I have never been able to find that James Watson (snr).
The Marquis of Ailsa and others funded this concern which was doomed to failure.
The Melbourne James Watson married again when Elizabeth died in May 1847. The second wife Anne Hawker gave details on his 1869 death certificate which were incorrect.
I have even visited the area in SCotland and stood outside the Keillor steading - which is now being developed. The origin of the Australian Keillor is often misquoted, giving Hugh as James's father. Hence my original post.
However I have never seen the reference you have given to Margaret Rose being a possible sister. I will pursue these new thoughts
Thank you