Hi Rosie
That is good that you have some further link for the Masson brothers going off to Australia.
Can't see so far the link to Robert Norrie (rather than Rossie as you said) being an uncle to Mary b. 1892. His wife Margaret has the surname of Anderson not Craig...although she could be a half sister maybe? Hopefully things and relationships will be clearer with more info along the way. Maggie Anderson married Robert Norrie in 1885 in Edinburgh from the index.
Just for more background, this is the Robert Norrie and Margaret mentioned earlier, in 1891:
Robert Norrie 38 tailor and clothier b. Newburgh Fife
Margaret Norrie 33 wife b. Leith Midlothian
Alexander M Norrie 30 brother tailor b. Newburgh Fife
Address: 3 Holyrood Quad, Glasgow/Kelvin
Monica