You may need to check further sources to try and pick up on a thread taking to you to James in Melbourne from these family lines we have here. A really useful source, which Gali mentioned in the other post, is Wills & Testaments. At least three showing from what we have so far:
William Watson 2 Jan 1835. Tenant at AUCHTERTYRE. FORFAR SHERIFF COURT. Ref. SC47/40/10 - 5 pages
Hugh WATSON Esq., 19 April 1866 Sometime at KEILLOR, afterwards residing at THE DEN, near PERTH at PERTH SHERIFF COURT. Ref. SC49/31/81 -45 pages
Can't easily see anything for Grandfather George in terms of Wills & Testaments, whose death we have in 1813 from what has been mentioned.
Mrs Elizabeth Carmichael ROSE - 17 July 1857, Alias HUNTER, residing in CARNOUSTIE, relict of James ROSE, Esquire of FLEMINGTON at DUNDEE SHERIFF COURT. Ref. SC45/31/13 - 17 pages
I know exchange rates can make things complicated, but you can view/download all these three wills online on SP for £7GB/30 units. Incredibly good value. You pay 10 units to view each will, regardless of how many pages there are. In this case, particularly for Hugh, they are substantial documents.
Also, cannot see a Will entry showing for James Rose of Flemington. Some sources show him deceased by 1828 (no further details). On this generation of Roses, Margaret is showing as eldest daughter and Jane Ramsay Rose as the youngest daughter of James Rose. Elizabeth before c.1813, with youngest Jane being around 1813. This fits with what I have seen for Elizabeth. One possible further sister here
https://familysearch.org/pal:/MM9.1.1/XYJ1-KMGDid James Watson and Elizabeth Rose have any children up to her early death? What about from James' marriage to Anne Hawker? What parents' details did Anne Hawker show for James from his 1869 death reg.?
Monica